Web/JavaScript/Reference/Global objects/String/padStart

The padStart() method pads the current string with another string (multiple times, if needed) until the resulting string reaches the given length. The padding is applied from the start of the current string.

Syntax

str.padStart(targetLength [, padString])

Parameters

targetLength: The length of the resulting string once the current str has been padded. If the value is less than str.length, then str is returned as-is.
padString Optional: The string to pad the current str with. If padString is too long to stay within the targetLength, it will be truncated from the end. The default value is " " (U+0020 'SPACE').

Return value

A String of the specified targetLength with padString applied from the start.

Examples

Basic examples

'abc'.padStart(10);         // "       abc"
'abc'.padStart(10, "foo");  // "foofoofabc"
'abc'.padStart(6,"123465"); // "123abc"
'abc'.padStart(8, "0");     // "00000abc"
'abc'.padStart(1);          // "abc"

Fixed width string number conversion

// Javascript version of: (unsigned)
//  printf "%0*d" width num
function leftFillNum(num, targetLength) {
    return num.toString().padStart(targetLength, 0);
}

const num = 123;
console.log(leftFillNum(num, 5));
// expected output: "00123"

Specifications

Specification
ECMAScript (ECMA-262)The definition of 'String.prototype.padStart' in that specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`padStart`	Chrome Full support 57	Edge Full support 15	Firefox Full support 48	IE No support No	Opera Full support 44	Safari Full support 10	WebView Android Full support 57	Chrome Android Full support 57	Firefox Android Full support 48	Opera Android Full support 43	Safari iOS Full support 10	Samsung Internet Android Full support 7.0	nodejs Full support 8.0.0 Full support 8.0.0 Full support 7.0.0 Disabled' Disabled' From version 7.0.0: this feature is behind the `--harmony` runtime flag.

Legend

Full support: Full support
No support: No support
User must explicitly enable this feature.': User must explicitly enable this feature.