indexOf vs includes

Compares String.prototype.indexOf against String.prototype.includes for substring searches.

Shazzer Elite

Created Jul 4, 2026

Updated Jul 4, 2026

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CategoryJavaScript Syntax

VisibilityPublic

TypePERF

CharsetUTF-8

Code used before fuzz:

var iterations = 2000000;0x0D
var s = "hello world";

Snippet A:

s.indexOf("world") !== -1

Snippet B:

s.includes("world")

Sample payloads

s.indexOf("world") !== -1

s.includes("world")

Snippet A

s.indexOf("world") !== -1

Snippet B

s.includes("world")

Browser	Snippet A	Snippet B	Winner
1stSafari26.5.2	4.00 ms	5.00 ms	Snippet A1.25× faster
2ndChrome150.0.7871.47	7.90 ms	7.90 ms	Tie
3rdFirefox152.0	8.00 ms	8.00 ms	Tie

Median of 5 trials × 2,000,000 iterations per snippet.