trim(), trimStart(), trimEnd()

Syntax

str.trim()
str.trimStart()
str.trimEnd()

Examples

const input = "   hello world   ";

console.log(trim = input.trim());       // "hello world"
console.log(input.trimStart());          // "hello world   " - only leading removed
console.log(input.trimEnd());            // "   hello world" - only trailing removed

function validateUsername(input) {
  const trimmed = input.trim();
  if (trimmed.length === 0) {
    return "Username cannot be empty or just whitespace";
  }
  return `Valid username: ${trimmed}`;
}

console.log(validateUsername("   ")); // "Username cannot be empty or just whitespace"
console.log(validateUsername("  alice  ")); // "Valid username: alice"

Best practices

• Always trim() user input before validation checks (like checking for empty strings) to catch whitespace-only submissions
• Trim input before storing it, to avoid inconsistent data caused by accidental leading/trailing spaces
• Use trimStart()/trimEnd() specifically when only one side needs cleaning, such as preserving intentional trailing formatting
• Remember trim() only removes whitespace characters (spaces, tabs, newlines), not other characters like punctuation

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