http: lazy allocate cookies array

ronag · aduh95 · commit 99a85213bf38 · 2026-02-19T18:46:22.000+01:00
PR-URL: #59734 Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com> Reviewed-By: Ethan Arrowood <ethan@arrowood.dev> Reviewed-By: Tim Perry <pimterry@gmail.com> Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com> Reviewed-By: Jake Yuesong Li <jake.yuesong@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de> Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
diff --git a/lib/_http_outgoing.js b/lib/_http_outgoing.js
@@ -731,20 +731,22 @@ OutgoingMessage.prototype.setHeaders = function setHeaders(headers) {
   // We also cannot safely split by comma.
   // To avoid setHeader overwriting the previous value we push
   // set-cookie values in array and set them all at once.
-  const cookies = [];
+  let cookies = null;
 
   for (const { 0: key, 1: value } of headers) {
     if (key === 'set-cookie') {
       if (ArrayIsArray(value)) {
+        cookies ??= [];
         cookies.push(...value);
       } else {
+        cookies ??= [];
         cookies.push(value);
       }
       continue;
     }
     this.setHeader(key, value);
   }
-  if (cookies.length) {
+  if (cookies != null) {
     this.setHeader('set-cookie', cookies);
   }
 

Original file line number	Diff line number	Diff line change
`@@ -731,20 +731,22 @@ OutgoingMessage.prototype.setHeaders = function setHeaders(headers) {`
`731`	`731`	`// We also cannot safely split by comma.`
`732`	`732`	`// To avoid setHeader overwriting the previous value we push`
`733`	`733`	`// set-cookie values in array and set them all at once.`
`734`		`- const cookies = [];`
	`734`	`+ let cookies = null;`
`735`	`735`
`736`	`736`	`for (const { 0: key, 1: value } of headers) {`
`737`	`737`	`if (key === 'set-cookie') {`
`738`	`738`	`if (ArrayIsArray(value)) {`
	`739`	`+ cookies ??= [];`
`739`	`740`	`cookies.push(...value);`
`740`	`741`	`} else {`
	`742`	`+ cookies ??= [];`
`741`	`743`	`cookies.push(value);`
`742`	`744`	`}`
`743`	`745`	`continue;`
`744`	`746`	`}`
`745`	`747`	`this.setHeader(key, value);`
`746`	`748`	`}`
`747`		`- if (cookies.length) {`
	`749`	`+ if (cookies != null) {`
`748`	`750`	`this.setHeader('set-cookie', cookies);`
`749`	`751`	`}`
`750`	`752`