String.prototype.match()

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[""]。

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

If the regular expression does not include the g flag, str.match() will return the same result as RegExp.exec() (en-US). The returned 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 Array containing all matched substrings rather than match objects. Captured groups are not returned. If there were no matches, the method returns null.

• If you need to know if a string matches a regular expression RegExp, use RegExp.test() (en-US).
• If you only want the first match found, you might want to use RegExp.exec() (en-US) instead.
• if you want to obtain capture groups and the global flag is set, you need to use RegExp.exec() (en-US) instead.

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.

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']

When the parameter is a string or a number, it is implicitly converted to a 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"]

• flags was a non standard second argument only available in Gecko : str.match(regexp, flags)
• Starting with Gecko 27, this method has been adjusted to conform with the ECMAScript specification. When match() is called with a global regular expression, the RegExp.lastIndex (en-US) property (if specified) will be reset to 0 (Firefox bug 501739).
• Starting with Gecko 39, the non-standard flags argument is deprecated and throws a console warning (Firefox bug 1142351).
• Starting with Gecko 47, the non-standard flags argument is no longer supported in non-release builds and will soon be removed entirely (Firefox bug 1245801).
• Starting with Gecko 49, the non-standard flags argument is no longer supported (Firefox bug 1108382).

• RegExp
• RegExp.prototype.exec() (en-US)
• RegExp.prototype.test() (en-US)