How to write regular expressions in js

Regular Expression (English: Regular Expression, often abbreviated as regex, regexp or RE in code) uses a single string to describe and match a series of string search patterns that conform to a certain syntactic rule.

Search mode can be used for text search and text replacement.

A regular expression is a search pattern formed by a sequence of characters.

When you search for data in text, you can use search patterns to describe what you want to query.

A regular expression can be a simple character, or a more complex pattern.

Regular expressions can be used for all text search and text replacement operations.

Syntax

/正则表达式主体/修饰符(可选)

The modifier is optional.

In JavaScript, regular expressions are commonly used in two string methods: search() and replace().

search() method is used to retrieve a specified substring in a string, or to retrieve a substring that matches a regular expression, and returns the starting position of the substring.

replace() method is used to replace some characters with other characters in a string, or replace a substring that matches a regular expression.

search() method uses regular expressions

Example:

Search for "php" string using regular expressions , and is not case-sensitive:

var str = "Visit php!"; 
var n = str.search(/php/i);

The output result is:

6

The search() method uses the string

The search method can take a string as parameter. String parameters will be converted into regular expressions:

Example: Retrieve the substring of "php" in the string:

var str = "Visit php!"; 
var n = str.search("php");

replace() method uses regular expressions

Example: Use regular expressions and case-insensitive to replace Microsoft in the string with Runoob:

var str = document.getElementById("demo").innerHTML; 
var txt = str.replace(/microsoft/i,"php");

The result output is:

Visit php!

replace() method uses string

replace() method will receive string as parameter:

var str = document.getElementById("demo").innerHTML; 
var txt = str.replace("Microsoft","php");

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