DevEquiv

    PHP trim() Equivalent in JavaScript

    JavaScript's String.prototype.trim() matches PHP's trim() for default whitespace trimming, but JavaScript's trim() has no second argument for a custom character set at all.

    Requires review

    PHP source
    trim()
    Closest JavaScript API
    String.prototype.trim()

    Main limitation: PHP's `trim($str, $charlist)` accepts a custom set of characters to strip; JavaScript's `.trim()` takes no arguments whatsoever — it always strips Unicode whitespace only. Stripping custom characters in JavaScript requires a regular expression, e.g. `str.replace(/^-+|-+$/g, '')`.

    How to use each function

    Before comparing the two, here's how trim() and String.prototype.trim() work on their own.

    PHP: trim()

    trim(string $string, string $characters = " \t\n\r\0\x0B"): string

    Strips characters from both the start and end of a string. With no second argument it removes the default whitespace set; passing $characters replaces that set entirely and supports range shorthand like 'a..z'. ltrim()/rtrim() strip only one side.

    Returns: The trimmed string.

    PHP 
    trim("  hello  "); // "hello"
trim("--hello--", "-"); // "hello"

    JavaScript: String.prototype.trim()

    str.trim()

    Removes whitespace from both ends of a string. Takes no arguments at all — there's no way to strip a custom character set directly; that requires a regular expression via .replace(). .trimStart()/.trimEnd() trim only one side (PHP's ltrim()/rtrim() equivalents).

    Returns: The trimmed string.

    JavaScript 
    "  hello  ".trim(); // "hello"

    Quick mapping

    PHP trim()
    Closest JavaScript API String.prototype.trim()

    How it differs

    • PHP's trim($str, $charlist) accepts a custom set of characters to strip; JavaScript's .trim() takes no arguments whatsoever — it always strips Unicode whitespace only. Stripping custom characters in JavaScript requires a regular expression, e.g. str.replace(/^-+|-+$/g, '').
    • JavaScript's .trim() whitespace definition (Unicode WhiteSpace and LineTerminator) is broader than PHP's default ASCII-only whitespace set, though for ordinary space/tab/newline input the results match.
    • PHP has ltrim()/rtrim(); JavaScript's equivalents are .trimStart()/.trimEnd() (with .trimLeft()/.trimRight() as older aliases) — the naming convention differs (start/end vs. left/right, though the aliases do use left/right).

    Examples

    Basic whitespace trim

    PHP 
    trim("  hello  ");
// "hello"
    JavaScript 
    "  hello  ".trim();
// "hello"
    Both strip leading/trailing whitespace with no arguments, and results match for ordinary whitespace.

    Custom character set requires a regex in JavaScript

    PHP 
    trim("--hello--", "-");
// "hello"
    JavaScript 
    "--hello--".replace(/^-+|-+$/g, "");
// "hello"
    JavaScript's trim() has no second argument, so a custom character set requires switching to replace() with a regular expression instead of a direct method-call translation.

    Edge cases

    Edge case

    If you need PHP's trim($str, $charlist) custom-character behavior in JavaScript, there is no direct method — you must build a regular expression, which is a genuinely different approach, not just a renamed function call.

    References

    • PHP Manual — trim — checked 2026-07-29
    • MDN Web Docs — String.prototype.trim() — checked 2026-07-29

    Last verified 2026-07-29.