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.


str.padStart(targetLength [, padString])


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.


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"


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

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
padStartChrome Full support 57Edge Full support 15Firefox Full support 48IE No support NoOpera Full support 44Safari Full support 10WebView Android Full support 57Chrome Android Full support 57Firefox Android Full support 48Opera Android Full support 43Safari iOS Full support 10Samsung Internet Android Full support 7.0nodejs Full support 8.0.0
Full support 8.0.0
Full support 7.0.0
Disabled From version 7.0.0: this feature is behind the --harmony runtime flag.


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User must explicitly enable this feature.

See also