replace() and replaceAll()

Syntax

str.replace(pattern, replacement)
str.replaceAll(pattern, replacement)

Examples

const text = "cat and cat and cat";

console.log(text.replace("cat", "dog"));
// "dog and cat and cat" - only the first match is replaced

const text = "cat and cat and cat";

console.log(text.replaceAll("cat", "dog"));
// "dog and dog and dog"

const prices = "Item1: $10, Item2: $25";

const discounted = prices.replace(/\$(\d+)/g, (match, amount) => {
  return `$${Math.round(amount * 0.9)}`;
});

console.log(discounted); // "Item1: $9, Item2: $23" (rounded)

Best practices

• Use replaceAll() for simple string replacements when you want every occurrence changed - it needs no regex or g flag
• Use replace() with a regex and the g flag if you need pattern-based (not literal string) global replacement
• Remember these methods return a new string - the original string is never modified, since strings are immutable
• Use a function as the replacement argument when the new value needs to be computed based on the match itself

At a glance

Purpose

Application logic and interaction

File extension

.js · .mjs

Runs in

Browsers and JavaScript runtimes

Usually used with

HTML, CSS and Web APIs

Specifications & further reading

• ECMAScript specification

Related JavaScript documentation