What are the new features in regular expressions?

This time I will bring you what are the new features in regular expressions, what are the notes when using the new features in regular expressions, the following are practical cases , let’s take a look.

New features of ES2015 regular expressions:

Based on the original regular expressions, ES2015 has enhanced support for four-byte unicode characters and other functions.

For more information on regular expressions, please refer to the regular expression tutorial section.

1. RegExpUsage of constructor:

Before ES2015, use the RegExp constructor to create a regular expression objectThere are two ways:

Creation method one:

var reg = new RegExp("antzone","g");

The first parameter of the constructor is the regular expression string body, and the second parameter is the regular expression modifier.
The above code is equivalent to the following code:

var regex = /antzone/g;

Creation method two:

var reg = new RegExp(/antzone/g);

If the parameter is not a regular expression string, there can only be one parameter; the following writing is wrong :

var reg = new RegExp(/antzone/,g);

It is not allowed to use the second parameter to set the regular expression modifier.
ES2015 changes this behavior, even if the first parameter is a regular expression object, the second parameter can also be specified:

var reg = new RegExp(/antzone/gi," g");

The regular expression modifier specified in the second parameter will override the modifier in the first parameter.

2. Regular methods for strings:

The match(), replace(), search() and split() methods related to regular expressions belong to strings object.
ES2015 has modified this. When these four methods are called, the instance method of the RegExp object is actually called internally.
(1).String.prototype.match calls RegExp.prototype[Symbol.match].
(2).String.prototype.replace calls RegExp.prototype[Symbol.replace]
(3).String.prototype.search calls RegExp.prototype[Symbol.search]
(3).String .prototype.split calls RegExp.prototype[Symbol.split]
For more information about Symbol, please refer to the ES2015 Symbol chapter.

3. Line-behind assertions (ES2016):

For line-behind assertions, please refer to the chapter on regular expression zero-width assertions.

4. New modifiers:

Modifier	Description
u modifier	This modifier identifies the ability to correctly handle Unicode characters larger than \uFFFF.
y modifier	specifies that matching can only start from the position specified by the lastIndex attribute. If the match fails, subsequent characters will not be tried again.

5. New attributes:

Attribute	Description
sticky attribute	Returns a Boolean value to identify whether the y modifier is set.
flags attribute	Returns the modifiers of the regular expression.

6. New method:

Method	Description
RegExp.escape()(ES2016)

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

Recommended reading:

Regular Expressions Detailed explanation of the use of \W metacharacters (with code)

Regular Expressions Detailed introduction to character classes

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