This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.
The padStart()
method pads the current string with another string (repeated, if needed) so that the resulting string reaches the given length. The padding is applied from the start (left) of the current string.
Syntax
str.padStart(targetLength [, padString])
Parameters
targetLength
- The length of the resulting string once the current string has been padded. If the value is lower than the current string's length, the current string will be returned as is.
padString
Optional- The string to pad the current string with. If this string is too long to stay within the target length, it will be truncated and the left-most part will be applied. The default value for this parameter is " " (U+0020).
Return value
A String
of the specified length with the pad string applied from the start.
Examples
'abc'.padStart(10); // " abc" 'abc'.padStart(10, "foo"); // "foofoofabc" 'abc'.padStart(6,"123465"); // "123abc" 'abc'.padStart(8, "0"); // "00000abc" 'abc'.padStart(1); // "abc"
Polyfill
Running the following code before any other code will create String.prototype.padStart()
if it's not natively available.
// https://github.com/uxitten/polyfill/blob/master/string.polyfill.js // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padStart if (!String.prototype.padStart) { String.prototype.padStart = function padStart(targetLength,padString) { targetLength = targetLength>>0; //floor if number or convert non-number to 0; padString = String(padString || ' '); if (this.length > targetLength) { return String(this); } else { targetLength = targetLength-this.length; if (targetLength > padString.length) { padString += padString.repeat(targetLength/padString.length); //append to original to ensure we are longer than needed } return padString.slice(0,targetLength) + String(this); } }; }
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript Latest Draft (ECMA-262) The definition of 'String.prototype.padStart' in that specification. |
Draft | Initial definition in ECMAScript 2017. |
Browser compatibility
Feature | Chrome | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 57 | 15 | 48 (48) | No support | 44 | 10 |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | ? | 57 | 48.0 (48) | ? | ? | 10 |
See also
Document Tags and Contributors
Tags:
Contributors to this page:
regiskuckaertz,
wkillerud,
wildtron,
AtomicNoggin,
uxitten,
arai,
Loadmaster,
David_Gilbertson,
bsara,
YoruNoHikage,
Sebastianz,
SphinxKnight
Last updated by:
regiskuckaertz,