JavaScript RegExp : Object

constructor

RegExp represents a regular expression that can be used for searching and extracting parts of Strings.

RegExp(pattern : String, [flags : String]) : RegExp

Constructs a new RegExp for the specified pattern. If flags contains 'g', this.global will be set to true. If flags contains 'i', this.ignoreCase will be set to true. If flags contains 'm', this.multiline will be set to true. RegExps can also be constructed using /pattern/flags syntax.

Example:

// The following are equivalent
var x = /pattern/i;
var y = RegExp('pattern', 'i');
var z = new RegExp('pattern', 'i');

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Constructors

new RegExp(pattern : String, [flags : String]) : RegExp

Same as RegExp(pattern, flags).

Spec

Instance Properties

global : Boolean

true if the RegExp was created with the 'g' flag. Global RegExps will match each place this.source occurs in the string, not just the first match.

Example:

console.log('abcba'.replace(/b/, 'X'));
console.log('abcba'.replace(/b/g, 'X'));

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ignoreCase : Boolean

true if the RegExp was created with the 'i' flag. IgnoreCase RegExps will do case insensitive matching.

Example:

console.log(/hello/.test('Hello'));
console.log(/hello/i.test('Hello'));

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lastIndex : Number

The starting index into the string for the next search. Is automatically set to the index after a successful match. This property only applies if the RegExp is global.

Example:

var regexp = /foo|bar|baz/g;
console.log(regexp.exec('foo bar baz')[0]);
console.log(regexp.lastIndex);
regexp.lastIndex = 5;
console.log(regexp.exec('foo bar baz')[0]);

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multiline : Boolean

true if the RegExp was created with the 'm' flag. Multiline RegExps will match '^' to the beginning of lines as well as the beginning of the string and match '$' to the end of lines as well as the end of the string.

Example:

var str = 'hello\nworld';
console.log(/^world/.test(str));
console.log(/^world/m.test(str));

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source : String

The pattern of this regular expression.

Example:

var regexp = /(\d\d\d)-(\d\d\d\d)/;
console.log(regexp);
console.log(regexp.source);

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Instance Methods

exec(str : String) : Array

If this matches str, returns a new Array with item 0 equal to the portion of str that matched the regular expression, item 1 equal to the first capturing group in this, item 2 equal to the second capturing group in this, and so on. If this doesn't match str, returns null.

Example:

var regexp = /(\d\d\d)-(\d\d\d\d)/;
var result = regexp.exec('call me: 555-4385');
if (result) {
  console.log(result[0]);
  console.log(result[1]);
  console.log(result[2]);
}

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test(str : String) : Boolean

Returns true if this matches str.

Example:

var regexp = /(\d\d\d)-(\d\d\d\d)/;
console.log(regexp.test('555-4385'));
console.log(regexp.test('KL5-4385'));

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