--- title: String.prototype.substring() slug: Web/JavaScript/Reference/Global_Objects/String/substring translation_of: Web/JavaScript/Reference/Global_Objects/String/substring ---
{{JSRef}}

The substring() method returns a subset of a string between one index and another, or through the end of the string.

Syntax

str.substring(indexStart[, indexEnd])

Parametreler

indexStart
An integer between 0 and the length of the string, specifying the offset into the string of the first character to include in the returned substring.
indexEnd
Optional. An integer between 0 and the length of the string, which specifies the offset into the string of the first character not to include in the returned substring.

Dönen değer

A new string containing the extracted section of the given string.

Açıklama

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

If indexStart is greater than indexEnd, then the effect of substring() is as if the two arguments were swapped; for example, str.substring(1, 0) == str.substring(0, 1).

Örnekler

Using substring()

The following example uses substring() to display characters from the string 'Mozilla':

var anyString = 'Mozilla';

// Displays 'Moz'
console.log(anyString.substring(0, 3));
console.log(anyString.substring(3, 0));

// Displays 'lla'
console.log(anyString.substring(4, 7));
console.log(anyString.substring(4));
console.log(anyString.substring(7, 4));

// Displays 'Mozill'
console.log(anyString.substring(0, 6));

// Displays 'Mozilla'
console.log(anyString.substring(0, 7));
console.log(anyString.substring(0, 10));

Using substring() with length property

The following example uses the substring() method and {{jsxref("String.length", "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
var anyString = 'Mozilla';
var anyString4 = anyString.substring(anyString.length - 4);
console.log(anyString4);

// Displays 'zilla' the last 5 characters
var anyString = 'Mozilla';
var anyString5 = anyString.substring(anyString.length - 5);
console.log(anyString5);

Replacing a substring within a string

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' into 'Brave New Web'.

// Replaces oldS with newS in the string fullS
function replaceString(oldS, newS, fullS) {
  for (var 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 {{jsxref("String.prototype.replace()")}}.

Specifications

Specification Status Comment
{{SpecName('ES1')}} {{Spec2('ES1')}} Implemented in JavaScript 1.0.
{{SpecName('ES5.1', '#sec-15.5.4.15', 'String.prototype.substring')}} {{Spec2('ES5.1')}}  
{{SpecName('ES6', '#sec-string.prototype.substring', 'String.prototype.substring')}} {{Spec2('ES6')}}  
{{SpecName('ESDraft', '#sec-string.prototype.substring', 'String.prototype.substring')}} {{Spec2('ESDraft')}}  

Tarayıcı uyumluluğu

{{Compat("javascript.builtins.String.substring")}}

Ayrıca bakınız