String.prototype.padStart()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2017.
padStart()
會將用給定用於填充的字串,以重複的方式,插入到目標字串的起頭(左側),直到目標字串到達指定長度。
Syntax
js
str.padStart(targetLength [, padString])
Parameters
targetLength
-
目標字串被填充後的長度。如果此參數小於原字串的長度,那將直接返回原字串。
padString
選擇性-
用來填充的字串。如果填充字串太長,則由左側開始,擷取所需要的長度。此參數預設值是空白 " " (U+0020).
Return value
目標字串被填充到指定長度後,所得的新字串。
Examples
js
"abc".padStart(10); // " abc"
"abc".padStart(10, "foo"); // "foofoofabc"
"abc".padStart(6, "123465"); // "123abc"
規範
Specification |
---|
ECMAScript® 2025 Language Specification # sec-string.prototype.padstart |
瀏覽器相容性
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padStart |
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- Full support
- Full support
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