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String concat vs array join

Compares building a string with += concatenation against Array.prototype.join for assembling many pieces.

Shazzer Master

Created Jul 4, 2026

Updated Sep 5, 2026

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CategoryJavaScript Syntax

VisibilityPublic

TypePERF

CharsetUTF-8

Code used before fuzz:

var iterations = 20000;
var parts=Array.from({length:100},function(_,i){return "x"+i});

Snippet A:

var r="";for(var i=0;i<parts.length;i++){r+=parts[i]}

Snippet B:

parts.join("")

Sample payloads

var r="";for(var i=0;i<parts.length;i++){r+=parts[i]}

parts.join("")

Snippet A

var r="";for(var i=0;i<parts.length;i++){r+=parts[i]}

Snippet B

parts.join("")

Browser	Snippet A	Snippet B	Winner
1stMicrosoft Edge153.0.4234.32	5.80 ms	8.80 ms	Snippet A1.52× faster
2ndFirefox156.0	9.00 ms	7.00 ms	Snippet B1.29× faster
3rdChrome153.0.8010.53	9.80 ms	12.30 ms	Snippet A1.26× faster
4thSafari26.6.2