benchmark: spread operator benchmark

Benchmark comparing `util._extend()`, `Object.assign()`, and the spread operator for object assignment. `util._extend()` still wins currently. PR-URL: #18442 Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: Weijia Wang <[email protected]> Reviewed-By: Luigi Pinca <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Yuta Hiroto <[email protected]>

Author: jasnell

benchmark/es/spread-assign.js

@@ -0,0 +1,46 @@
+'use strict';
+
+constcommon=require('../common.js');
+constutil=require('util');
+
+constbench=common.createBenchmark(main,{
+method: ['spread','assign','_extend'],
+count: [5,10,20],
+millions: [1]
+});
+
+functionmain({ millions, context, count, rest, method }){
+constn=millions*1e6;
+
+constsrc={};
+for(letn=0;n<count;n++)
+src[`p${n}`]=n;
+
+letobj;// eslint-disable-line
+leti;
+
+switch(method){
+case'':
+// Empty string falls through to next line as default, mostly for tests.
+case'_extend':
+bench.start();
+for(i=0;i<n;i++)
+obj=util._extend({},src);
+bench.end(n);
+break;
+case'assign':
+bench.start();
+for(i=0;i<n;i++)
+obj=Object.assign({},src);
+bench.end(n);
+break;
+case'spread':
+bench.start();
+for(i=0;i<n;i++)
+obj={ ...src};
+bench.end(n);
+break;
+default:
+thrownewError('Unexpected method');
+}
+}