lib: add getLazy() method to internal/util

joyeecheung · targos · commit 00bdb72b6ec2 · 2023-11-10T09:49:22.000+01:00
This patch adds a getLazy() method to facilitate initialize-once lazy loading in the internals. PR-URL: #45849 Backport-PR-URL: #46425 Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com> Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
diff --git a/lib/internal/util.js b/lib/internal/util.js
@@ -691,6 +691,24 @@ function isArrayBufferDetached(value){
 return false;
 }
 
+/**
+ * Helper function to lazy-load an initialize-once value.
+ * @template T Return value of initializer
+ * @param{()=>T} initializer Initializer of the lazily loaded value.
+ * @returns{()=>T}
+ */
+function getLazy(initializer){
+ let value;
+ let initialized = false;
+ return function(){
+ if (initialized === false){
+ value = initializer();
+ initialized = true;
+ }
+ return value;
+ };
+}
+
 // Setup user-facing NODE_V8_COVERAGE environment variable that writes
 // ScriptCoverage objects to a specified directory.
 function setupCoverageHooks(dir){
@@ -713,6 +731,7 @@ function setupCoverageHooks(dir){
 }
 
 module.exports ={
+ getLazy,
 assertCrypto,
 cachedResult,
 convertToValidSignal,

-Original file line number
+Diff line change
 returnfalse;
+}
 +/**
 + * Helper function to lazy-load an initialize-once value.
 + * @template T Return value of initializer
 + * @param{()=>T} initializer Initializer of the lazily loaded value.
 + * @returns{()=>T}
 + */
 +functiongetLazy(initializer){
 +letvalue;
 +letinitialized=false;
 +returnfunction(){
 +if(initialized===false){
 +value=initializer();
 +initialized=true;
 +}
 +returnvalue;
 +};
 +}
++
 // Setup user-facing NODE_V8_COVERAGE environment variable that writes
 // ScriptCoverage objects to a specified directory.
 functionsetupCoverageHooks(dir){
+}
 module.exports={
 + getLazy,
  assertCrypto,
  cachedResult,
  convertToValidSignal,