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

The match() method retrieves the matches when matching a string against a regular expression.

Syntax

str.match(regexp)

Parameters

regexp
一個正規表達式的物件。 若傳入一個非正規表達式的物件obj，則會視為傳入 new RegExp(obj)。若只呼叫match()而沒有傳入任何參數，則會回傳內含一個空字串的陣列，即[""]。

Return value

If the string matches the expression, it will return an {{jsxref("Array")}} containing the entire matched string as the first element, followed by any results captured in parentheses. If there were no matches, {{jsxref("null")}} is returned.

Description

If the regular expression does not include the g flag, str.match() will return the same result as {{jsxref("RegExp.prototype.exec()", "RegExp.exec()")}}. The returned {{jsxref("Array")}} has an extra input property, which contains the original string that was parsed. In addition, it has an index property, which represents the zero-based index of the match in the string.

If the regular expression includes the g flag, the method returns an {{jsxref("Array")}} containing all matched substrings rather than match objects. Captured groups are not returned. If there were no matches, the method returns {{jsxref("null")}}.

See also: RegExp methods

Examples

Using match()

In the following example, match() is used to find 'Chapter' followed by 1 or more numeric characters followed by a decimal point and numeric character 0 or more times. The regular expression includes the i flag so that upper/lower case differences will be ignored.

var str = 'For more information, see Chapter 3.4.5.1';
var re = /see (chapter \d+(\.\d)*)/i;
var found = str.match(re);

console.log(found);

// logs [ 'see Chapter 3.4.5.1',
//        'Chapter 3.4.5.1',
//        '.1',
//        index: 22,
//        input: 'For more information, see Chapter 3.4.5.1' ]

// 'see Chapter 3.4.5.1' is the whole match.
// 'Chapter 3.4.5.1' was captured by '(chapter \d+(\.\d)*)'.
// '.1' was the last value captured by '(\.\d)'.
// The 'index' property (22) is the zero-based index of the whole match.
// The 'input' property is the original string that was parsed.

Using global and ignore case flags with match()

The following example demonstrates the use of the global and ignore case flags with match(). All letters A through E and a through e are returned, each its own element in the array.

var str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
var regexp = /[A-E]/gi;
var matches_array = str.match(regexp);

console.log(matches_array);
// ['A', 'B', 'C', 'D', 'E', 'a', 'b', 'c', 'd', 'e']

Using match() with no parameter

var str = "Nothing will come of nothing.";

str.match();   // returns [""]

A non-RegExp object as the parameter

When the parameter is a string or a number, it is implicitly converted to a {{jsxref("RegExp")}} by using new RegExp(obj). If it is a positive number with a positive sign,the RegExp() method will ignore the positive sign. 

var str1 = "NaN means not a number. Infinity contains -Infinity and +Infinity in JavaScript.",
    str2 = "My grandfather is 65 years old and My grandmother is 63 years old.",
    str3 = "The contract was declared null and void.";
str1.match("number");   // "number" is a string. returns ["number"]
str1.match(NaN);        // the type of NaN is the number. returns ["NaN"]
str1.match(Infinity);   // the type of Infinity is the number. returns ["Infinity"]
str1.match(+Infinity);  // returns ["Infinity"]
str1.match(-Infinity);  // returns ["-Infinity"]
str2.match(65);         // returns ["65"]
str2.match(+65);        // A number with a positive sign. returns ["65"]
str3.match(null);       // returns ["null"]

Specifications

Specification Status Comment
{{SpecName('ES3')}} {{Spec2('ES3')}} Initial definition. Implemented in JavaScript 1.2.
{{SpecName('ES5.1', '#sec-15.5.4.10', 'String.prototype.match')}} {{Spec2('ES5.1')}}  
{{SpecName('ES6', '#sec-string.prototype.match', 'String.prototype.match')}} {{Spec2('ES6')}}  
{{SpecName('ESDraft', '#sec-string.prototype.match', 'String.prototype.match')}} {{Spec2('ESDraft')}}  

Browser compatibility

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

Firefox-specific notes

See also