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A library of zero-dependency npm modules that do just one thing. A guilt-free alternative to those bulkier utility libraries. Ideal for PWA development or whenever bytes are precious.
We welcome contributions. Please follow our contribution guidelines.
A REPL for every utility (powered by RunKit)
- TRADEOFFS.md -- When to use Just (and when not to).
- The Zen of Dependency-Free -- Why I wrote Just.
All packages support ES module or Common JS syntax without requiring transpilation
// esm (node / bundler) import clone from 'just-clone'; // esm (native browser code) import clone from './node_modules/just-clone/index.mjs'; // cjs const clone = require('just-clone'); 
We've now added TypeScript definitions and tests for every Just utility
Most utilities still work with any platform that supports ES5, but these are the earliest versions guranteed to support every utility. For guidance, any platform that supports spread in array literals will work with Just.
| Chrome | Safari | Firefox | Edge | Node | Mobile Safari | Android Chrome |
|---|---|---|---|---|---|---|
| 46 | 8 | 16 | 12 | 6.0 | 8 | 46 |
- Collections{}[]
- Objects{}
- Arrays []
- Statistics Σ
- Strings ""
- Numbers +-
- Functions =>
npm install just-diffyarn add just-diffReturn an object representing the difference between two other objects Pass converter to format as http://jsonpatch.com
import{diff}from'just-diff';constobj1={a: 4,b: 5};constobj2={a: 3,b: 5};constobj3={a: 4,c: 5};diff(obj1,obj2);[{"op": "replace","path": ['a'],"value": 3}]diff(obj2,obj3);[{"op": "remove","path": ['b']},{"op": "replace","path": ['a'],"value": 4}{"op": "add","path": ['c'],"value": 5}]// using converter to generate jsPatch standard pathsimport{diff,jsonPatchPathConverter}from'just-diff'diff(obj1,obj2,jsonPatchPathConverter);[{"op": "replace","path": '/a',"value": 3}]diff(obj2,obj3,jsonPatchPathConverter);[{"op": "remove","path": '/b'},{"op": "replace","path": '/a',"value": 4}{"op": "add","path": '/c',"value": 5}]// arraysconstobj4={a: 4,b: [1,2,3]};constobj5={a: 3,b: [1,2,4]};constobj6={a: 3,b: [1,2,4,5]};diff(obj4,obj5);[{"op": "replace","path": ['a'],"value": 3}{"op": "replace","path": ['b',2],"value": 4}]diff(obj5,obj6);[{"op": "add","path": ['b',3],"value": 5}]// nested pathsconstobj7={a: 4,b: {c: 3}};constobj8={a: 4,b: {c: 4}};constobj9={a: 5,b: {d: 4}};diff(obj7,obj8);[{"op": "replace","path": ['b','c'],"value": 4}]diff(obj8,obj9);[{"op": "replace","path": ['a'],"value": 5}{"op": "remove","path": ['b','c']}{"op": "add","path": ['b','d'],"value": 4}]npm install just-diff-applyyarn add just-diff-applyApply a diff object to an object. Pass converter to apply a http://jsonpatch.com standard patch
import{diffApply}from'just-diff-apply';constobj1={a: 3,b: 5};diffApply(obj1,[{"op": "remove","path": ['b']},{"op": "replace","path": ['a'],"value": 4},{"op": "add","path": ['c'],"value": 5}]);obj1;//{a: 4, c: 5}constobj2={a: 3,b: 5};diffApply(obj2,[{"op": "move","from": ['a'],"path": ['c']},]);obj2;//{b: 5, c: 3}// using converter to apply jsPatch standard paths// see http://jsonpatch.comimport{diffApply,jsonPatchPathConverter}from'just-diff-apply'constobj3={a: 3,b: 5};diffApply(obj3,[{"op": "remove","path": '/b'},{"op": "replace","path": '/a',"value": 4}{"op": "add","path": '/c',"value": 5}],jsonPatchPathConverter);obj3;//{a: 4, c: 5}// arrays (array key can be string or numeric)constobj4={a: 4,b: [1,2,3]};diffApply(obj4,[{"op": "replace","path": ['a'],"value": 3}{"op": "replace","path": ['b',2],"value": 4}{"op": "add","path": ['b',3],"value": 9}]);obj4;//{a: 3, b: [1, 2, 4, 9]}// nested pathsconstobj5={a: 4,b: {c: 3}};diffApply(obj5,[{"op": "replace","path": ['a'],"value": 5}{"op": "remove","path": ['b','c']}{"op": "add","path": ['b','d'],"value": 4}]);obj5;//{a: 5, b:{d: 4}}npm install just-compareyarn add just-compareCompare two collections
importcomparefrom'just-compare';// primitives: value1 === value2// functions: value1.toString == value2.toString// arrays: if length, sequence and values of properties are identical// objects: if length, names and values of properties are identicalcompare([1,[2,3]],[1,[2,3]]);// truecompare([1,[2,3],4],[1,[2,3]]);// falsecompare({a: 2,b: 3},{a: 2,b: 3});// truecompare({a: 2,b: 3},{b: 3,a: 2});// truecompare({a: 2,b: 3,c: 4},{a: 2,b: 3});// falsecompare({a: 2,b: 3},{a: 2,b: 3,c: 4});// falsecompare([1,[2,{a: 4}],4],[1,[2,{a: 4}]]);// falsecompare([1,[2,{a: 4}],4],[1,[2,{a: 4}],4]);// truecompare(NaN,NaN);// truenpm install just-cloneyarn add just-cloneDeep copies objects, arrays, maps and sets
// Deep copies objects and arrays, doesn't clone functionsimportclonefrom'just-clone';vararr=[1,2,3];varsubObj={aa: 1};varobj={a: 3,b: 5,c: arr,d: subObj};varobjClone=clone(obj);arr.push(4);objClone.d.bb=2;obj;//{a: 3, b: 5, c: [1, 2, 3, 4], d:{aa: 1}}objClone;//{a: 3, b: 5, c: [1, 2, 3], d:{aa: 1, bb: 2}}npm install just-pluck-ityarn add just-pluck-itPluck a property from each member of a collection
importpluckfrom'just-pluck-it';pluck([{a:1,b:2},{a:4,b:3},{a:2,b:5}],'a');// [1, 4, 2]pluck({x: {a:1,b:2},y: {a:4,b:3},z: {a:2,b:5}},'a');//{x: 1, y: 4, z: 2}npm install just-flushyarn add just-flushReturns a copy of an array or object with null/undefined members removed
importflushfrom'just-flush';flush([1,undefined,2,null,3,NaN,0]);// [1, 2, 3, NaN, 0]flush([true,null,false,true,[null],undefined]);// [true, false, true, [null]]flush({a: 2,b: null,c: 4,d: undefined});//{a: 2, c: 4}flush('something');// undefinedflush();// undefinednpm install just-extendyarn add just-extendExtend an object
importextendfrom'just-extend';varobj={a: 3,b: 5};extend(obj,{a: 4,c: 8});//{a: 4, b: 5, c: 8}obj;//{a: 4, b: 5, c: 8}varobj={a: 3,b: 5};extend({},obj,{a: 4,c: 8});//{a: 4, b: 5, c: 8}obj;//{a: 3, b: 5}vararr=[1,2,3];varobj={a: 3,b: 5};extend(obj,{c: arr});//{a: 3, b: 5, c: [1, 2, 3]}arr.push(4);obj;//{a: 3, b: 5, c: [1, 2, 3, 4]}vararr=[1,2,3];varobj={a: 3,b: 5};extend(true,obj,{c: arr});//{a: 3, b: 5, c: [1, 2, 3]}arr.push(4);obj;//{a: 3, b: 5, c: [1, 2, 3]}extend({a: 4,b: 5});//{a: 4, b: 5}extend({a: 4,b: 5},3);{a: 4,b: 5}extend({a: 4,b: 5},true);{a: 4,b: 5}extend('hello',{a: 4,b: 5});// throwsextend(3,{a: 4,b: 5});// throwsnpm install just-mergeyarn add just-mergeShallow assign. Like just-extend but without deep copy option.
importmergefrom'just-merge';letobj={a: 3,b: 5};merge(obj,{a: 4,c: 8});//{a: 4, b: 5, c: 8}obj;//{a: 4, b: 5, c: 8}letobj={a: 3,b: 5};merge({},obj,{a: 4,c: 8});//{a: 4, b: 5, c: 8}obj;//{a: 3, b: 5}letarr=[1,2,3];letobj={a: 3,b: 5};merge(obj,{c: arr});//{a: 3, b: 5, c: [1, 2, 3]}arr.push[4];obj;//{a: 3, b: 5, c: [1, 2, 3, 4]}merge({a: 4,b: 5});//{a: 4, b: 5}merge(3,{a: 4,b: 5});// throwsmerge({a: 4,b: 5},3);// throwsmerge({a: 4,b: 5},{b: 4,c: 5},'c');// throwsnpm install just-valuesyarn add just-valuesReturn property values as an array
constvalues=require('just-values');values({a: 4,c: 8});// [4, 8]values({a: {aa: 2},b: {bb: 4}});// [{aa: 2},{bb: 4}]values({});// []values([1,2,3]);// [1, 2, 3]values(function(a,b){returna+b;});// []values(newString('hello'));// ['h', 'e', 'l', 'l', 'o']values(1);// throws exceptionvalues(true);// throws exceptionvalues(undefined);// throws exceptionvalues(null);// throws exceptionnpm install just-entriesyarn add just-entriesReturn object entries as an array of [key, value] pairs
importentriesfrom'just-entries';// Object:entries({c: 8,a: 4});// [['c', 8], ['a', 4]]entries({b: {bb: 4},a: {aa: 2}});// [['b',{bb: 4}], ['a',{aa: 2}]]entries({});// []// Array:entries([{c: 8},{a: 4}]);// [[0,{c: 8}], [1,{a: 4}]]entries(['À','mauvais','ouvrier','point','de','bon','outil'])// [[0, 'À'], [1, 'mauvais'] ... [6, 'outil']]entries([]);// []npm install just-pickyarn add just-pickCopy an object but with only the specified keys
importpickfrom'just-pick';varobj={a: 3,b: 5,c: 9};pick(obj,['a','c']);//{a: 3, c: 9}pick(obj,'a','c');//{a: 3, c: 9}pick(obj,['a','b','d']);//{a: 3, b: 5}pick(obj,['a','a']);//{a: 3}npm install just-omityarn add just-omitCopy an object but omit the specified keys
importomitfrom'just-omit';varobj={a: 3,b: 5,c: 9};omit(obj,['a','c']);//{b: 5}omit(obj,'a','c');//{b: 5}omit(obj,['a','b','d']);//{c: 9}omit(obj,['a','a']);//{b: 5, c: 9}npm install just-is-emptyyarn add just-is-emptyReturn true if object has no enumerable key values
importisEmptyfrom'just-is-empty';isEmpty({a: 3,b: 5})// falseisEmpty([1,2])// falseisEmpty(newSet([1,2,2]))// falseisEmpty((newMap()).set('a',2))// falseisEmpty({})// trueisEmpty([])// trueisEmpty(newSet())// trueisEmpty(newMap())// trueisEmpty('abc')// falseisEmpty('')// trueisEmpty(0)// trueisEmpty(1)// trueisEmpty(true)// trueisEmpty(Symbol('abc'));// trueisEmpty(//); // trueisEmpty(newString('abc'));// falseisEmpty(newString(''));// trueisEmpty(newBoolean(true));// trueisEmpty(null)// trueisEmpty(undefined)// truenpm install just-is-circularyarn add just-is-circularReturn true if object has a circular reference NOTE: not supported in IE or microsoft edge
importisCircularfrom'just-is-circular';consta={};a.b=a;isCircular(a);// trueconsta={};a.b={c: a};isCircular(a);// trueconsta={};a.b={c: 4};isCircular(a);// falseconsta=[];a.push(a);isCircular(a);// trueisCircular({});// falseisCircular('hi');// falseisCircular(undefined);// falsenpm install just-is-primitiveyarn add just-is-primitiveDetermine if a value is a primitive value
importisPrimitivefrom'just-is-primitive';isPrimitive('hi')// trueisPrimitive(3)// trueisPrimitive(true)// trueisPrimitive(false)// trueisPrimitive(null)// trueisPrimitive(undefined)// trueisPrimitive(Symbol())// trueisPrimitive({})// falseisPrimitive([])// falseisPrimitive(function(){})// falseisPrimitive(newDate())// falseisPrimitive(/a/)// falsenpm install just-filter-objectyarn add just-filter-objectFilter an object
importfilterfrom'just-filter';// returns a new object containing those original properties for which the predicate returns truthyfilter({a: 3,b: 5,c: 9},(key,value)=>value<6);//{a: 3, b: 5}filter({a1: 3,b1: 5,a2: 9},(key,value)=>key[0]=='a');//{a1: 3, a2: 9}filter({a: 3,b: 5,c: null},(key,value)=>value);//{a: 3, b: 5}npm install just-map-objectyarn add just-map-objectMap an object, passing key and value to predicates
importmapfrom'just-map-object';// DEPRECATED: use just-map-valuesmap({a: 3,b: 5,c: 9},(key,value)=>value+1);//{a: 4, b: 6, c: 10}map({a: 3,b: 5,c: 9},(key,value)=>key);//{a: 'a', b: 'b', c: 'c'}map({a: 3,b: 5,c: 9},(key,value)=>key+value);//{a: 'a3', b: 'b5', c: 'c9'}```npm install just-map-valuesyarn add just-map-valuesMap an object, predicate updates values, receives (value, key, object)
importmapfrom'just-map-values';// predicate updates values, receives (value, key, obj)map({a: 3,b: 5,c: 9},(value)=>value+1);//{a: 4, b: 6, c: 10}map({a: 3,b: 5,c: 9},(value,key)=>value+key);//{a: 3a, b: 5b, c: 9c}map({a: 3,b: 5,c: 9},(value,key,obj)=>obj.b);//{a: 5, b: 5, c: 5}npm install just-map-keysyarn add just-map-keysMap an object, predicate updates keys, receives (value, key, object)
importmapfrom'just-map-keys';// predicate updates keys, receives (value, key, object)map({a: 'cow',b: 'sheep',c: 'pig'},(value)=>value);//{cow: 'cow', sheep: 'sheep', pig: 'pig'}map([4,5,6],(value,key)=>key+1);//{1: 4, 2: 5, 3: 6}map({a: 3,b: 5,c: 9},(value,key)=>key+value);//{a3: 3, b5: 5, c9: 9}map({a: 3,b: 5,c: 9},(value,key,obj)=>obj.b+value+key);//{'8a': 3, '10b': 5, '14c': 9}npm install just-deep-map-valuesyarn add just-deep-map-valuesReturns an object with values at all depths mapped according to the provided function
importdeepMapValuesfrom'just-deep-map-values';constsquareFn=(number)=>number*number;deepMapValues({a: 1,b: {c: 2,d: {e: 3}}},squareFn);// =>{a: 1, b:{c: 4, d:{e: 9 }}}npm install just-reduce-objectyarn add just-reduce-objectReduce an object
importreducefrom'just-reduce-object';// applies a function against an accumulator and each key-value pairs of the object// to reduce it to a single valuereduce({a: 3,b: 5,c: 9},(acc,key,value,index,keys)=>{acc[value]=key;returnacc;},{});//{3: 'a', 5: 'b', 9: 'c'}reduce({a: 3,b: 5,c: 9},(acc,key,value,index,keys)=>{acc+=value;returnacc;});// 17npm install just-safe-getyarn add just-safe-getGet value at property, don't throw if parent is undefined
importgetfrom'just-safe-get';constobj={a: {aa: {aaa: 2}},b: 4};get(obj,'a.aa.aaa');// 2get(obj,['a','aa','aaa']);// 2get(obj,'b.bb.bbb');// undefinedget(obj,['b','bb','bbb']);// undefinedget(obj.a,'aa.aaa');// 2get(obj.a,['aa','aaa']);// 2get(obj.b,'bb.bbb');// undefinedget(obj.b,['bb','bbb']);// undefinedget(obj.b,'bb.bbb',5);// 5get(obj.b,['bb','bbb'],true);// trueget(null,'a');// undefinedget(undefined,['a']);// undefinedget(null,'a',42);// 42get(undefined,['a'],42);// 42constobj={a: {}};constsym=Symbol();obj.a[sym]=4;get(obj.a,sym);// 4npm install just-safe-setyarn add just-safe-setSet value at property, create intermediate properties if necessary
importsetfrom'just-safe-set';constobj1={};set(obj1,'a.aa.aaa',4);// trueobj1;//{a:{aa:{aaa: 4}}}constobj2={};set(obj2,['a','aa','aaa'],4);// trueobj2;//{a:{aa:{aaa: 4}}}constobj3={a: {aa: {aaa: 2}}};set(obj3,'a.aa.aaa',3);// trueobj3;//{a:{aa:{aaa: 3}}}constobj5={a: {}};constsym=Symbol();set(obj5.a,sym,7);// trueobj5;//{a:{Symbol(): 7}}npm install just-typeofyarn add just-typeofType inferer
importtypeOffrom'just-typeof';typeOf({});// 'object'typeOf([]);// 'array'typeOf(function(){});// 'function'typeOf(/a/);// 'regexp'typeOf(newDate());// 'date'typeOf(null);// 'null'typeOf(undefined);// 'undefined'typeOf('a');// 'string'typeOf(1);// 'number'typeOf(true);// 'boolean'npm install just-flip-objectyarn add just-flip-objectFlip the keys and values
importflipfrom'just-flip-object';// flip the key and valueflip({a: 'x',b: 'y',c: 'z'});//{x: 'a', y: 'b', z: 'c'}flip({a: 1,b: 2,c: 3});//{'1': 'a', '2': 'b', '3': 'c'}flip({a: false,b: true});//{false: 'a', true: 'b'}npm install just-hasyarn add just-hasReturn a boolen indicating the existence of a deep property, don't throw if parent is undefined
importhasfrom'just-has';constobj={a: {aa: {aaa: 2}},b: 4};has(obj,'a.aa.aaa');// truehas(obj,['a','aa','aaa']);// truehas(obj,'b.bb.bbb');// falsehas(obj,['b','bb','bbb']);// falsehas(obj.a,'aa.aaa');// truehas(obj.a,['aa','aaa']);// truehas(obj.b,'bb.bbb');// falsehas(obj.b,['bb','bbb']);// falsehas(null,'a');// falsehas(undefined,['a']);// falseconstobj={a: {}};constsym=Symbol();obj.a[sym]=4;has(obj.a,sym);// truenpm install just-cartesian-productyarn add just-cartesian-productTakes an input of an array of arrays and returns their Cartesian product.
importcartesianProductfrom'just-cartesian-product';cartesianProduct([[1,2],['a','b']]);// [[1, 'a'], [1, 'b'], [2, 'a'], [2, 'b']]cartesianProduct([[1,2],['a','b','c']]);// [[1, 'a'], [1, 'b'], [1, 'c'], [2, 'a'], [2, 'b'], [2, 'c']]cartesianProduct([]);// []cartesianProduct();// throwsnpm install just-uniqueyarn add just-uniqueDedupes an array
importuniquefrom'just-unique';unique([1,2,3,2,3,4,3,2,1,3]);// [1, 2, 3, 4]vara={a: 3};varb={b: 4};varc={c: 5};unique([a,a,b,c,b]);// [a, b, c]unique([1,'1',2,'2',3,2]);// [1, '1', 2, '2', 3]// declaring sorted array for performanceunique([1,1,'1',2,2,5,'5','5'],true);// [1, '1', 2, 5, '6']// declaring strings array for performanceunique(['a','c','b','c','a'],false,true);// ['a', 'b', 'c']npm install just-flatten-ityarn add just-flatten-itReturn a flattened array
importflattenfrom'just-flatten-it';flatten([[1,[2,3]],[[4,5],6,7,[8,9]]]);// [1, 2, 3, 4, 5, 6, 7, 8, 9]flatten([[1,[2,3]],[[4,5],6,7,[8,9]]],1);// [1, [2, 3], [[4, 5], 6, 7, [8, 9]]]npm install just-indexyarn add just-indexReturn an object from an array, keyed by the value at the given id
importindexfrom'just-index';index([{id: 'first',val: 1},{id: 'second',val: 2}],'id');//{first:{id: 'first', val: 1}, second:{id: 'second', val: 2}}index([{id: 'first',val: 1},null],'id');//{first:{id: 'first', val: 1}}index([],'id');//{}index([],null);// undefinedindex({},'id');// undefinednpm install just-insertyarn add just-insertInserts a sub-array into an array starting at the given index. Returns a copy
importinsertfrom'just-insert';insert([1,2,5,6],['a','c','e'],2);// [1, 2, 'a', 'c', 'e', 5, 6]insert([1,2,5,6],'a',2);// [1, 2, 'a', 5, 6]insert([1,2,5,6],['a','c','e'],0);// ['a', 'c', 'e', 1, 2, 5, 6]insert([1,2,5,6],['a','c','e']);// ['a', 'c', 'e', 1, 2, 5, 6]npm install just-intersectyarn add just-intersectReturn the intersect of two arrays
importintersectfrom'just-intersect';intersect([1,2,5,6],[2,3,5,6]);// [2, 5, 6]intersect([1,2,2,4,5],[3,2,2,5,7]);// [2, 5] npm install just-compactyarn add just-compactReturns a copy of an array with falsey values removed
importcompactfrom'just-compact';compact([1,null,2,undefined,null,NaN,3,4,false,5]);// [1, 2, 3, 4, 5]compact([1,2,[],4,{}]);// [1, 2, [], 4,{}]compact([]);// []compact({});// throwsnpm install just-lastyarn add just-lastReturn the last member of an array
importlastfrom'just-last';last([1,2,3,4,5]);// 5last([{a: 1},{b: 1},{c: 1}]);//{c: 1}last([true,false,[true,false]]);// [true, false]last();// undefinedlast([]);// undefinedlast(null);// undefinedlast(undefined);// undefinednpm install just-tailyarn add just-tailReturn all but the first element of an array
importtailfrom'just-tail';tail([1,2,3,4,5]);// [2, 3, 4, 5]tail([{a: 1},{b: 1},{c: 1}]);// [{b: 1},{c: 1}]tail([true,false,[true,false]]);// [false, [true, false]]tail([]);// []tail();// undefinedtail(null);// undefinedtail(undefined);// undefinednpm install just-randomyarn add just-randomReturn a randomly selected element in an array
importrandomfrom'just-random';random([1,2,3]);// one of [1, 2, 3], at randomnpm install just-shuffleyarn add just-shuffleReturn the elements of an array in random order
importshufflefrom'just-shuffle';shuffle([1,2,3]);// array with original elements randomly sortedshuffle([1,2,3],{shuffleAll: true});// array with original elements randomly sorted and all in new postionsshuffle([]);// []shuffle([1]);// [1]shuffle();// throwsshuffle(undefined);// throwsshuffle(null);// throwsshuffle({});// throwsnpm install just-splityarn add just-splitSplits array into groups of n items each
importsplitfrom'just-split';split([]);// []split([1,2,3,4,5]);// [[1, 2, 3, 4, 5]]split([1,2,3,4,5,6,7,8,9],3);// [[1, 2, 3], [4, 5, 6], [7, 8, 9]]split([1,2,3,4,5,6,7,8,9],'3');// [[1, 2, 3], [4, 5, 6], [7, 8, 9]]split(['a','b','c','d','e'],2);// [['a', 'b'], ['c', 'd'], ['e']]split([1,2,3,4,5,6,7,8],3);// [[1, 2, 3], [4, 5, 6], [7, 8]]npm install just-split-atyarn add just-split-atSplits an array into two at a given position
importsplitAtfrom'just-split-at';splitAt([1,2,3,4,5],2);// [[1, 2], [3, 4, 5]]splitAt([{a: 1},{b: 1},{c: 1}],-1);// [[{a: 1},{b: 1}], [{c: 1}]]splitAt([],2);// [[], []]splitAt(null,1);// throwssplitAt(undefined,1);// throwsnpm install just-order-byyarn add just-order-byProduces a new array, sorted in given order
importorderByfrom'just-order-by';orderBy([10,1,5,20,15,35,30,6,8]);// [1, 5, 6, 8, 10, 15, 20, 30, 35]orderBy([{user: 'fabio',details: {city: 'Milan',age: 34}},{user: 'max',details: {city: 'Munich',age: 29}},{user: 'zacarias',details: {city: 'Sao Paulo',age: 44}},{user: 'robert',details: {city: 'Manchester',age: 28}},{user: 'max',details: {city: 'Zurich',age: 38}},],[{property(v){returnv.details.age;},},]);/*[{user: 'robert', age: 28},{user: 'max', age: 29},{user: 'fabio', age: 34},{user: 'klaus', age: 38},{user: 'zacarias', age: 44},]*/orderBy([{user: 'fabio',age: 34},{user: 'max',age: 29},{user: 'zacarias',age: 44},{user: 'robert',age: 28},{user: 'klaus',age: 38},],[{property: 'user',},]);/*[{user: 'fabio', age: 34},{user: 'klaus', age: 38},{user: 'max', age: 29},{user: 'robert', age: 28},{user: 'zacarias', age: 44},]*/orderBy([{user: 'fabio',age: 34},{user: 'max',age: 29},{user: 'zacarias',age: 44},{user: 'moris',age: 28},{user: 'max',age: 38},],[{property: 'user',order: 'desc',},{property(v){returnv.age;},},]);/*[{ user: 'zacarias', age: 44 },{ user: 'moris', age: 28 },{ user: 'max', age: 29 },{ user: 'max', age: 38 },{ user: 'fabio', age: 34 }]*/npm install just-sort-byyarn add just-sort-byProduces a new array, sorted in ascending order
importsortByfrom'just-sort-by';sortBy([10,1,5,20,15,35,30,6,8]);// [1, 5, 6, 8, 10, 15, 20, 30, 35]sortBy([{user: 'fabio',details: {city: "Milan",age: 34}},{user: 'max',details: {city: "Munich",age: 29}},{user: 'zacarias',details: {city: "Sao Paulo",age: 44}},{user: 'robert',details: {city: "Manchester",age: 28}},{user: 'klaus',details: {city: "Zurich",age: 38}},],function(o){returno.details.age;});/*[{user: 'robert', age: 28},{user: 'max', age: 29},{user: 'fabio', age: 34},{user: 'klaus', age: 38},{user: 'zacarias', age: 44},]*/sortBy([{user: 'fabio',age: 34},{user: 'max',age: 29},{user: 'zacarias',age: 44},{user: 'robert',age: 28},{user: 'klaus',age: 38},],'user');/*[{user: 'fabio', age: 34},{user: 'klaus', age: 38},{user: 'max', age: 29},{user: 'robert', age: 28},{user: 'zacarias', age: 44},]*/npm install just-partitionyarn add just-partitionElements satisfying predicate added to first array, remainder added to second
importpartitionfrom'just-partition';partition([1,5,2,4,3],n=>n>3);// [[5, 4],[1, 2, 3]]partition(['a',2,3,'3'],x=>typeofx=='string');// [['a', '3'],[2, 3]]partition([1,2,3,4],x=>typeofx=='number');// [[1, 2, 3, 4],[]]partition([1,2,3,4],x=>typeofx=='string');// [[], [1, 2, 3, 4]]partition([],n=>n>3);// [[], []]partition({a: 1,b: 2},n=>n>1);// throwspartition(null,n=>n>1);// throwspartition(undefined,n=>n>1);// throwsnpm install just-permutationsyarn add just-permutationsReturns all permutations of the length N of the elements of the given Array
importpermutationsfrom'just-permutations';permutations([1,2,3]);// [[1, 2, 3], [2, 1, 3], [2, 3, 1], [1, 3, 2], [3, 1, 2], [3, 2, 1]]permutations([]);// []permutations();// throwsnpm install just-rangeyarn add just-rangeGenerate a range array for numbers
importrangefrom'just-range';range(1,5);// [1, 2, 3, 4]range(5);// [0, 1, 2, 3, 4]range(-5);// [0, -1, -2, -3, -4]range(0,20,5)// [0, 5, 10, 15]npm install just-removeyarn add just-removeRemoves one array from another
importremovefrom'just-remove';remove([1,2,3,4,5,6],[1,3,6]);// [2, 4, 5]npm install just-unionyarn add just-unionReturns the union of two arrays
importunionfrom'just-union';union([1,2,5,6],[2,3,4,6]);// [1, 2, 5, 6, 3, 4]npm install just-zip-ityarn add just-zip-itReturns an array of grouped elements, taking n-th element from every given array
importzipfrom'just-zip-it';zip([1,2,3]);// [[1], [2], [3]]zip([1,2,3],['a','b','c']);// [[1, 'a'], [2, 'b'], [3, 'c']]zip([1,2],['a','b'],[true,false]);//[[1, 'a', true], [2, 'b', false]]zip(undefined,{},false,1,'foo');// []zip([1,2],['a','b'],undefined,{},false,1,'foo');// [[1, 'a'], [2, 'b']]zip([1,2,3],['a','b'],[true]);// [[1, 'a', true], [2, 'b', undefined], [3, undefined, undefined]]npm install just-group-byyarn add just-group-byReturn a grouped object from array
importgroupByfrom'just-group-by';groupBy([6.1,4.2,6.3],Math.floor);//{'4': [4.2], '6': [6.1, 6.3] }groupBy([1,2,3,4,5,6,7,8],function(i){returni%2});//{'0': [2, 4, 6, 8], '1': [1, 3, 5, 7] }npm install just-meanyarn add just-meanThe mean (average) value in an array
importmeanfrom'just-mean';mean([1,2,3,2,4,1]);// 2.1666666667mean(3,2,1);// 2mean([4]);// 4mean(['3',2]);// throwsmean();// throwsnpm install just-medianyarn add just-medianReturn the median value of an array of numbers
importmedianfrom'just-median';median([1,2,3,4,5]);// 3median([3,-1,2]);// 2median([9,14,14,200,15]);// 14median(1,2,4,3);// 2.5median(['3',2,1]);// throwsmedian();// throwsnpm install just-modeyarn add just-modeReturn the most frequently occuring number(s)
importmodefrom'just-mode';mode([1,2,3,2]);// 2mode(4,4,1,4);// 4mode(100,100,101,101);// [100, 101]mode(4,3,2,1);// [1, 2, 3, 4]mode(['1',2,2,1,2]);// throwsmode(null);// throwsnpm install just-percentileyarn add just-percentileReturn the value at the given percentile (using linear interpolation)
importpercentilefrom'just-percentile';percentile([1,2,3],0);// 1percentile([1,2,3],0.5);// 2percentile([1,2,3],1);// 3// See https://en.wikipedia.org/wiki/Percentile (linear interpolation method)percentile([15,20,35,40,50],0.05);// 15percentile([15,20,35,40,50],0.3);// 20percentile([15,20,35,40,50],0.4);// 27.5percentile([15,20,35,40,50],0.95);// 50percentile(1,2,3,50);// throwspercentile(['1',2,3],50);// throwspercentile([],50);// throwsnpm install just-varianceyarn add just-varianceReturn the standard deviation of an array or numeric argument list
importvariancefrom'just-variance';variance([1,2,3,2,4,1]);// 1.3666666667variance(3,2,1);// 1variance([100,100,100.1,100]);// 0.0025variance(1,2,3,4,5,-6);// 15.5variance([4]);// throwsvariance(['3',2]);// throwsvariance(NaN,NaN);// throwsvariance();// throwsnpm install just-standard-deviationyarn add just-standard-deviationReturn the standard deviation of an array or numeric argument list
importstandardDeviationfrom"just-standard-deviation";standardDeviation([1,2,3,2,4,1]);// 1.16904519standardDeviation(3,2,1);// 1standardDeviation([100,100,100.1,100]);// 0.05standardDeviation(1,2,3,4,5,-6);// 3.9370039standardDeviation([4]);// throwsstandardDeviation(["3",2]);// throwsstandardDeviation(NaN,NaN);// throwsstandardDeviation();// throwsnpm install just-skewnessyarn add just-skewnessReturn the skewness of an array or numeric argument list using Pearson's second skewness coefficient
importskewnessfrom"just-skewness";// Using Pearson's second skewness coefficientskewness(3,2,1);// 0skewness([1,2,3,2,4,1]);// 0.4276994613841504skewness(1,2,3,4,5,-6);// -0.762000762001143skewness([1,2,3,4,9]);// 0.7705935588815224skewness([4]);// throwsskewness(["3",2]);// throwsskewness(NaN,NaN);// throwsskewness();// throwsnpm install just-templateyarn add just-templateInterpolate a string with variables
importtemplatefrom'just-template';vardata={a: {aa: {aaa: 'apple',bbb: 'pear'},bb: 'orange'},b: 'plum'};template('2{{a.aa.aaa}}s, a{{a.aa.bbb}}, 3{{a.bb}}s and a{{b}}. Yes 1{{a.aa.bbb}}.',data);// '2 apples, a pear, 3 oranges and a plum. Yes 1 pear.'npm install just-truncateyarn add just-truncateTruncate a string with a custom suffix
truncate('when shall we three meet again',9);// 'when s...'truncate('when shall we three meet again',10,' (etc)');// 'when (etc)'truncate('when shall we',15,);// 'when shall we'truncate('when shall we',15,'(more)');// 'when shall we'truncate('when shall we',10,' (etc etc etc)');// ' (etc etc etc)'npm install just-pruneyarn add just-prunePrune a string with whole words and a custom suffix
prune('when shall we three meet again',7);// 'when...'prune('when shall we three meet again',7,' (more)';// 'when (more)'prune('when shall we',15,);// 'when shall we'prune('when shall we',15,' (etc)');// 'when shall we'prune('when shall we',7,' (more)');// ' (more)'npm install just-squashyarn add just-squashRemove all spaces from a string, optionally remove escape sequences too
squash('the cat sat on the mat');// 'thecatsatonthemat'squash(' the cat sat on the mat ');// 'thecatsatonthemat'squash('\tthe cat\n sat \fon \vthe \rmat ');// '\tthecat\nsat\fon\vthe\rmat'squash('\tthe cat\n sat \fon \vthe \rmat ',true);// 'thecatsatonthemat'squash(`the catsat on the mat`,true);// thecatsatonthematnpm install just-left-padyarn add just-left-padAdd characters to the left of a string such that its total length is n
importleftPadfrom'just-left-pad';leftPad('hello',9);// ' hello'leftPad('hello',3);// 'hello'leftPad('hello',9,'.');// '....hello'leftPad('hello',9,'..');// '....hello'leftPad('hello',10,'ab');// 'bababhello'leftPad('hello',9,'\uD83D\uDC04');// '🐄🐄🐄🐄hello'leftPad('hello',10,'\uD83D\uDC11\uD83D\uDC04'),// '🐄🐑🐄🐑🐄hello'leftPad('hello',7,'🐄'),// '🐄🐄hello'leftPad(null,7);// throwsleftPad([],4,'*');// throwsleftPad('hello',4,true);// throwsleftPad('hello',-4,true);// throws leftPad('hello',2.3,true);// throws npm install just-right-padyarn add just-right-padAdd characters to the right of a string such that its total length is n
importrightPadfrom'just-right-pad';rightPad('hello',9);// 'hello 'rightPad('hello',3);// 'hello'rightPad('hello',9,'.');// 'hello....'rightPad('hello',9,'..');// 'hello....'rightPad('hello',10,'ab');// 'helloababa'rightPad('hello',9,'\uD83D\uDC04');// 'hello🐄🐄🐄🐄'rightPad('hello',10,'\uD83D\uDC11\uD83D\uDC04'),// 'hello🐑🐄🐑🐄🐑'rightPad('hello',7,'🐄'),// 'hello🐄🐄'rightPad(null,7);// throwsrightPad([],4,'*');// throwsrightPad('hello',4,true);// throwsrightPad('hello',-4,true);// throws rightPad('hello',2.3,true);// throws npm install just-camel-caseyarn add just-camel-caseConvert a string to camel case
importcamelCasefrom'just-camel-case';camelCase('the quick brown fox');// 'theQuickBrownFox'camelCase('the_quick_brown_fox');// 'theQuickBrownFox'camelCase('the-quick-brown-fox');// 'theQuickBrownFox'camelCase('theQuickBrownFox');// 'theQuickBrownFox'camelCase('thequickbrownfox');// 'thequickbrownfox'camelCase('the - quick * brown# fox');// 'theQuickBrownFox'camelCase('behold theQuickBrownFox');// 'beholdTheQuickBrownFox'camelCase('Behold theQuickBrownFox');// 'beholdTheQuickBrownFox'// all caps words are camel-casedcamelCase('The quick brown FOX'),'theQuickBrownFox');// all caps substrings >= 4 chars are camel-casedcamelCase('theQUickBrownFox');// 'theQUickBrownFox'camelCase('theQUIckBrownFox');// 'theQUIckBrownFox'camelCase('theQUICKBrownFox');// 'theQuickBrownFox'npm install just-kebab-caseyarn add just-kebab-caseConvert a string to kebab case
importkebabCasefrom'just-kebab-case';kebabCase('the quick brown fox');// 'the-quick-brown-fox'kebabCase('the-quick-brown-fox');// 'the-quick-brown-fox'kebabCase('the_quick_brown_fox');// 'the-quick-brown-fox'kebabCase('theQuickBrownFox');// 'the-quick-brown-fox'kebabCase('theQuickBrown Fox');// 'the-quick-brown-fox'kebabCase('thequickbrownfox');// 'thequickbrownfox'kebabCase('the - quick * brown# fox');// 'the-quick-brown-fox'kebabCase('theQUICKBrownFox');// 'the-q-u-i-c-k-brown-fox'npm install just-snake-caseyarn add just-snake-caseConvert a string to snake case
importsnakeCasefrom'just-snake-case';snakeCase('the quick brown fox');// 'the_quick_brown_fox'snakeCase('the-quick-brown-fox');// 'the_quick_brown_fox'snakeCase('the_quick_brown_fox');// 'the_quick_brown_fox'snakeCase('theQuickBrownFox');// 'the_quick_brown_fox'snakeCase('thequickbrownfox');// 'thequickbrownfox'snakeCase('the - quick * brown# fox');// 'the_quick_brown_fox'snakeCase('theQUICKBrownFox');// 'the_q_u_i_c_k_brown_fox'npm install just-pascal-caseyarn add just-pascal-caseConvert a string to pascal case
importpascalCasefrom'just-pascal-case';pascalCase('the quick brown fox');// 'TheQuickBrownFox'pascalCase('the_quick_brown_fox');// 'TheQuickBrownFox'pascalCase('the-quick-brown-fox');// 'TheQuickBrownFox'pascalCase('theQuickBrownFox');// 'TheQuickBrownFox'pascalCase('thequickbrownfox');// 'Thequickbrownfox'pascalCase('the - quick * brown# fox');// 'TheQuickBrownFox'pascalCase('theQUICKBrownFox');// 'TheQUICKBrownFox'npm install just-capitalizeyarn add just-capitalizeCapitalize the first character of a string
importcapitalizefrom'just-capitalize';/* capitalize('capitals'); // 'Capitals' capitalize('Capitals'); // 'Capitals' capitalize('many words'); // 'Many words' capitalize('!exclaim'); // '!exclaim'*/npm install just-replace-allyarn add just-replace-allReplace all occurrences of a string within a string with another string
importreplaceAllfrom'just-replace-all';/* replaceAll('hello, world', 'l', 'q'); // 'heqqo, worqd' replaceAll('hello, world', 'l', 'qq'); // 'heqqqqo, worqqd' replaceAll('hello, world', 'll', 'q'); // 'heqo, world' replaceAll('hello, world', '', 'q'); // 'hello, world' replaceAll('hello, world', 'l', ''); // 'heo, word' replaceAll('hello, world', null, 'q'); // 'hello, world' replaceAll('hello, world', 'l'); // throw replaceAll('hello, world'); // throw replaceAll(); // throw replaceAll(null, 'l', 'q'); // throw replaceAll('hello, world', null, 'q'); // throw replaceAll('hello, world', 'l', null); // throw*/npm install just-clampyarn add just-clampRestrict a number within a range
importclampfrom'just-clamp';varn=5;clamp(1,n,12);// 5clamp(3,n,1);// 3clamp(8,n,9);// 8clamp(0,n,0);// 0varn=-5;clamp(1,n,12);// 1clamp(-7,n,-8);// -7clamp(NaN,n,8);// NaNclamp(3,n,NaN);// NaN clamp(3,NaN,8);// NaN clamp(undefined,n,8);// throwsclamp(3,n,'h');// throws clamp(3,false,8);// throws npm install just-is-primeyarn add just-is-primeCheck if number is prime
importisPrimefrom 'just-is-prime; /* isPrime(1); // false isPrime(2); // true isPrime(17); // true isPrime(10); // false isPrime(); // throws isPrime(null); // throws isPrime("js"); // throws isPrime({}); // throws isPrime(function(){}); // throws isPrime([]); // throws*/npm install just-moduloyarn add just-moduloModulo of a number and a divisor
importmodulofrom'just-modulo';modulo(7,5);// 2modulo(17,23);// 17modulo(16.2,3.8);// 1modulo(5.8,3.4);//2.4modulo(4,0);// 4modulo(-7,5);// 3modulo(-2,15);// 13modulo(-5.8,3.4);// 1modulo(12,-1);// NaNmodulo(-3,-8);// NaNmodulo(12,'apple');// NaNmodulo('bee',9);// NaNmodulo(null,undefined);// NaNnpm install just-random-integeryarn add just-random-integerProduces a random integer within a given range
importrandomfrom'just-random-integer';random();// Returns either 0 or 1random(5);// Returns a random integer between 0 and 5 (inclusively)random(3,10);// Returns a random integer between 3 and 10 (inclusively)random(-5.8,10.4);// Returns a random integer between -5 and 10 (inclusively)npm install just-composeyarn add just-composeReturn a function composed of 2 or more functions
importcomposefrom'just-compose';constsqRootBiggest=compose(Math.max,Math.sqrt,Math.trunc);sqRootBiggest(10,5);// 3sqRootBiggest(7,0,16);// 4npm install just-curry-ityarn add just-curry-itReturn a curried function
importcurryfrom'just-curry-it';functionadd(a,b,c){returna+b+c;}curry(add)(1)(2)(3);// 6curry(add)(1)(2)(2);// 5curry(add)(2)(4,3);// 9functionadd(...args){returnargs.reduce((sum,n)=>sum+n,0)}varcurryAdd4=curry(add,4)curryAdd4(1)(2,3)(4);// 10functionconverter(ratio,input){return(input*ratio).toFixed(1);}constcurriedConverter=curry(converter)constmilesToKm=curriedConverter(1.62);milesToKm(35);// 56.7milesToKm(10);// 16.2npm install just-demethodizeyarn add just-demethodizeTurn a method into a standalone function; the first arg becomes this
importdemethodizefrom'just-demethodize';consttrimFn=demethodize(''.trim);['hello ',' goodbye','hello again'].map(trimFn);// ['hello', 'goodbye', 'hello again']npm install just-flipyarn add just-flipFlip first two arguments of a function
importflipfrom'just-flip';flip(console.log)(1,2,3)// 2, 1, 3importmapfrom'just-map-object';importpartialfrom'just-partial';constnumbers={x: 5,y: 10};constflippedMap=flip(map);constdouble=partial(flippedMap,(undefined,number)=>number*2);double(numbers)//{x: 10, y: 20];npm install just-partial-ityarn add just-partial-itReturn a partial function
importpartialfrom'just-partial-it';constcubedRoot=partial(Math.pow,_,1/3);cubedRoot(64);// 4constgetRoot=partial(Math.pow,64);getRoot(1/2);// 8npm install just-pipeyarn add just-pipePass a value through a pipeline of functions
importpipefrom 'just-pipe pipe(3,a=>a+1,b=>b*2)// 8pipe('John Smith',a=>a.split(' '),b=>b.reverse(),c=>c[0])// 'Smith'npm install just-debounce-ityarn add just-debounce-itReturn a debounced function
importdebouncefrom"just-debounce-it";constfn1=debounce(()=>console.log("Hello"),500);fn1();fn1();fn1();// 500ms later logs 'hello' onceconstfn2=debounce(()=>console.log("Hello"),500,true);fn2();// logs hello immediatelyfn2();fn2();// 500ms later logs 'hello' onceconstfn3=debounce(()=>console.log("Hello"),500);fn3();fn3();fn3();fn3.cancel();// function cancelled before 'hello' is loggedconstfn4=debounce(()=>console.log("Hello"),500);fn4();fn4();fn4();fn4.flush();// immediately invoke the debounced functionnpm install just-memoizeyarn add just-memoizeAn implementation of the memoize technique
importmemoizefrom'just-memoize';constsumByOne=memoize(function(value){returnvalue+1;});sumByOne(10);// Returns value returned by the functionsumByOne(10);// Cache hit!sumByOne(20);// Returns value returned by the functionsumByOne(20);// Cache hit!// Custom cache key (key defaults to JSON stringified arguments)varsum=memoize(function(a,b){returna+b;},function(a,b){return`${a}-${b}`;});sum(10,10);// Returns value returned by the functionsum(10,20);// Returns value returned by the functionsum(10,20);// Cache hit!npm install just-memoize-lastyarn add just-memoize-lastA memoize implementation that only caches the most recent evaluation
constmemoizeLast=require('just-memoize-last')constcompare=require('just-compare')constmaxValue=memoizeLast(function(arr){returnMath.max(...arr)},function(a,b){returncompare(a,b)});maxValue([1,2,3])// 3maxValue([1,2,3])// cache hit!maxValue([1,3,4])// 4maxValue([1,2,3])// 3npm install just-randomyarn add just-randomReturn a randomly selected element in an array
importrandomfrom'just-random';random([1,2,3]);// one of [1, 2, 3], at randomnpm install just-throttleyarn add just-throttleReturn a throttled function
importthrottlefrom'just-throttle';// no matter how many times the function is called, only invoke once within the given interval// options: // `leading`: invoke before interval// `trailing`: invoke afer intervalconstfn1=throttle(()=>console.log('hello'),500,{leading: true});setInterval(fn1,400);// logs 'hello' immediately and then every 500msconstfn2=throttle(()=>console.log('hello'),500,{trailing: true});setInterval(fn2,400);// logs 'hello' after 500ms and then every 500msconstfn3=throttle(()=>console.log('hello'),500,{leading: true,trailing: true});// forces trailing to falseconstfn4=throttle(()=>console.log('hello'),500,{leading: false});fn4();fn4();fn4();fn4.cancel();// function cancelled before 'hello' is loggedconstfn5=throttle(()=>console.log("Hello"),500);fn5();fn5();fn5();fn5.flush();// immediately invoke the throttled functionnpm install just-onceyarn add just-onceCreate a function that can only be invoked once
importoncefrom'just-once';constfn=once(()=>console.log('hello'));fn();// logs 'hello'fn();// does nothingRun all tests as a single test suite with
npm run test
Cross browser tests (via saucelabs) are in the sauce branch
