String Methods

JavaScript · Methods reference

JavaScript · Methods reference

📋 Overview

All common String prototype methods. Strings are immutable in JS.

🔧 Methods

Search & extract

Method	Description
`at(index)`	Char at index (negative OK)
`charAt(i)` / `charCodeAt(i)`	Character / UTF-16 code unit
`codePointAt(i)`	Full Unicode code point
`includes(search, position?)`	Substring test
`startsWith` / `endsWith`	Prefix/suffix test
`indexOf` / `lastIndexOf`	Index or -1
`match(regexp)` / `matchAll(regexp)`	RegExp matches
`search(regexp)`	Index of first RegExp match
`slice(start?, end?)`	Substring copy
`substring(start, end)`	Like slice but swaps negative to 0
`substr(start, length)`	Legacy — avoid; use slice

Transform

Method	Description
`toLowerCase()` / `toUpperCase()`	Case change
`trim()` / `trimStart()` / `trimEnd()`	Whitespace trim
`replace(search, replacement)`	First match or global with /g
`replaceAll(search, replacement)`	Replace all occurrences
`split(separator?, limit?)`	Split to array
`concat(...strings)`	Concatenate strings
`repeat(count)`	Repeat string n times
`padStart(len, pad?)` / `padEnd`	Pad to length
`normalize(form?)`	Unicode normalization
`localeCompare(other)`	Locale-aware compare
`toWellFormed()`	Fix lone surrogates (ES2024)

💡 Examples

See parent topic notes for runnable snippets; this page is the complete method index.

⚠️ Pitfalls

Mutating methods return None in Python — do not chain sort() / reverse() expecting a new list.
Default JS sort() compares strings — pass (a,b) => a-b for numbers.
SQL function names differ by dialect — verify Postgres vs MySQL docs.
Django QuerySet.update() skips save() signals and auto auto_now fields on models.

Strings

Promise Methods

JavaScript · Methods reference

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📋 Overview 🔧 Methods Search & extract Transform 💡 Examples ⚠️ Pitfalls 🔗 Related