String concat vs array join

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

Shazzer Master

Created byhackvertor

Created Jul 4, 2026

Updated Jul 4, 2026

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RSS

Detecting browser...

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("")

Performance results

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
1stChrome152.0.7977.65	6.10 ms	15.00 ms	Snippet A2.46× faster
2ndSafari26.5.2	9.00 ms	12.00 ms	Snippet A1.33× faster
3rdFirefox154.0	11.00 ms	16.00 ms	Snippet A1.45× faster
4thMicrosoft Edge152.0.4191.53

String concat vs array join

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

Shazzer Master

Created byhackvertor

Created Jul 4, 2026

Updated Jul 4, 2026

Unable to render tweet button

RSS

Detecting browser...

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("")

Performance results

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
1stChrome152.0.7977.65	6.10 ms	15.00 ms	Snippet A2.46× faster
2ndSafari26.5.2	9.00 ms	12.00 ms	Snippet A1.33× faster
3rdFirefox154.0	11.00 ms	16.00 ms	Snippet A1.45× faster
4thMicrosoft Edge152.0.4191.53

Median of 5 trials × 20,000 iterations per snippet.

Distributed Fuzzing

String concat vs array join

Sample payloads

Performance results

String concat vs array join

Sample payloads

Performance results