How to create a RegExp object

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How to create a RegExp object

In JavaScript, the first step in using a regular expression is to create a regular expression object, that is, a RegExp object.

The syntax for creating a RegExp object:

New RegExp (pattern,attributes)

Parameter description:

Parameter description

Required parameters for pattern. A string that specifies the pattern of the regular expression.

Attributes optional parameters. The match modifier can be "g", "I", "m", or a combination of them.

G: perform a global match (find all matches instead of stopping after the first match is found)

I: perform case-insensitive matching

M: perform multi-line matching.

For example, detect whether a string contains the letter "abc":

Var pattern=new RegExp ("abc")

Detect whether a string begins with the letter "abc":

Var pattern=new RegExp ("^ abc")

Detect whether a string is "abc":

Var pattern=new RegExp ("^ abc$")

The literal quantity of regular expression

JavaScript supports regular expressions literally, which makes the use of regular expressions more flexible.

Regular expression literal syntax:

/ pattern/attributes

The parameter description is the same as above.

For example, detect whether a string contains the letter "abc":

How to create a RegExp object

Var pattern=/abc/

Detect whether a string begins with the letter "abc":

Var pattern=/ ^ ABC /

Detect whether a string is "abc":

Var pattern=/ ^ ABC $/

Match modifier

The g modifier is used to perform a global match (to find all matches rather than stop after the first match is found). All major browsers support the g modifier.

For example, global matching of "is" in a string:

Var str= "Is this all there is?"

Var patt1=/is/g

The following tagged text shows where the string is matched:

Is this all there is?

The I modifier is used to perform case-insensitive matches. All major browsers support the I modifier.

For example, match the "itxueyuan" in a string regardless of case:

Var str= "Visit ItXueyuan"

Var patt1=/itxueyuan/i

The following tagged text shows where the string is matched:

Visit ItXueyuan

For example, make a case-insensitive global match of "itxueyuan" in a string:

Var str= "Itxueyuan is a website with various tutorials.Welcome to itxueyuan!"

Var patt1=/itxueyuan/ig

The following tagged text shows where the string is matched:

Itxueyuan is a website with various tutorials.Welcome to itxueyuan!

The m modifier is used to perform multiline matching. Before ECMAScript standardization, the m attribute was not supported. If pattern is a regular expression, not a string, you must omit this parameter.

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