在此页

• 句法
• 描述
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

substring() 方法返回一部分为 string 在起始和结束索引之间，或到字符串末尾。

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

句法

str.substring(indexStart[, indexEnd])
					

参数

indexStart

The index of the first character to include in the returned substring.

indexEnd 可选

The index of the first character to exclude from the returned substring.

返回值

A new string containing the specified part of the given string.

描述

substring() extracts characters from indexStart up to but not including indexEnd . In particular:

• 若 indexEnd 被省略， substring() extracts characters to the end of the string.
• 若 indexStart 等于 indexEnd , substring() returns an empty string.
• 若 indexStart 大于 indexEnd , then the effect of substring() is as if the two arguments were swapped; See example below.

Any argument value that is less than 0 or greater than stringName.length is treated as if it were 0 and stringName.length , respectively.

Any argument value that is NaN is treated as if it were 0 .

范例

使用 substring()

以下范例使用 substring() to display characters from the string 'Mozilla' :

let anyString = 'Mozilla'
// Displays 'M'
console.log(anyString.substring(0, 1))
console.log(anyString.substring(1, 0))
// Displays 'Mozill'
console.log(anyString.substring(0, 6))
// Displays 'lla'
console.log(anyString.substring(4))
console.log(anyString.substring(4, 7))
console.log(anyString.substring(7, 4))
// Displays 'Mozilla'
console.log(anyString.substring(0, 7))
console.log(anyString.substring(0, 10))
					

使用 substring() with length property

以下范例使用 substring() method and length property to extract the last characters of a particular string. This method may be easier to remember, given that you don't need to know the starting and ending indices as you would in the above examples.

// Displays 'illa' the last 4 characters
let anyString = 'Mozilla'
let anyString4 = anyString.substring(anyString.length - 4)
console.log(anyString4)
// Displays 'zilla' the last 5 characters
let anyString = 'Mozilla'
let anyString5 = anyString.substring(anyString.length - 5)
console.log(anyString5)
					

The difference between substring() and substr()

There's a subtle difference between the substring() and substr() methods, so you should be careful not to get them confused.

The arguments of substring() represent the starting and ending indexes, while the arguments of substr() represent the starting index and the number of characters to include in the returned string.

Furthermore, substr() is considered a legacy feature in ECMAScript and could be removed from future versions, so it is best to avoid using it if possible.

let text = 'Mozilla'
console.log(text.substring(2,5))  // => "zil"
console.log(text.substr(2,3))     // => "zil"
					

Differences between substring() and slice()

substring() and slice() methods are almost identical, but there are a couple of subtle differences between the two, especially in the way negative arguments are dealt with.

substring() method swaps its two arguments if indexStart 大于 indexEnd , meaning that a string is still returned. The slice() method returns an empty string if this is the case.

let text = 'Mozilla'
console.log(text.substring(5, 2))  // => "zil"
console.log(text.slice(5, 2))      // => ""
					

If either or both of the arguments are negative or NaN ， substring() method treats them as if they were 0 .

console.log(text.substring(-5, 2))  // => "Mo"
console.log(text.substring(-5, -2)) // => ""
					

slice() also treats NaN arguments as 0 , but when it is given negative values it counts backwards from the end of the string to find the indexes.

console.log(text.slice(-5, 2))   // => ""
console.log(text.slice(-5, -2))  // => "zil"
					

见 slice() page for more examples with negative numbers.

替换字符串中的子字符串

The following example replaces a substring within a string. It will replace both individual characters and substrings. The function call at the end of the example changes the string Brave New World to Brave New Web .

// Replaces oldS with newS in the string fullS
function replaceString(oldS, newS, fullS) {
  for (let i = 0; i < fullS.length; ++i) {
    if (fullS.substring(i, i + oldS.length) == oldS) {
      fullS = fullS.substring(0, i) + newS + fullS.substring(i + oldS.length, fullS.length)
    }
  }
  return fullS
}
replaceString('World', 'Web', 'Brave New World')
					

Note that this can result in an infinite loop if oldS is itself a substring of newS — for example, if you attempted to replace 'World' with 'OtherWorld' here.

A better method for replacing strings is as follows:

function replaceString(oldS, newS, fullS) {
  return fullS.split(oldS).join(newS)
}
					

The code above serves as an example for substring operations. If you need to replace substrings, most of the time you will want to use String.prototype.replace() .

规范

规范
ECMAScript (ECMA-262) 在该规范中的 String.prototype.substring 定义。

浏览器兼容性

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

更新 GitHub 上的兼容性数据

	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
substring	Chrome 1	Edge 12	Firefox 1	IE 3	Opera 3	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs 0.1.100

图例

完整支持

完整支持

另请参阅

• String.prototype.substr()
• String.prototype.slice()

元数据

• 最后修改： 2020 年 3 月 26 日

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