Regular expression js is an object

by the following code:

rer.test(str) Verify whether the string conforms to the reg rules whether there is a rer regular expression in the str string

str: string rer: regular expression

        var rer = /\./ //just point
        var reg = /Huaqing/
        var str = "Summer Solstice Bullfrog 666."
        var res = rer.test(str) //Verify that the string conforms to the reg rule if there is a rer regular expression in the str string
        console.log(res)

Another usage of the test function:

new RegExp creates a regular object

        var reg1 = new RegExp("summer solstice winter solstice")
        var str1 = "summer solstice winter solstice"
        var res = reg1.test(str1)
        console.log(res);

match

by the following code:

str2.match(reg2) : str2 is a string, reg2 is a regular expression to be matched in a string, opposite to test

/[a-c][a-c]/ig means to take two numbers. The first is the number between a-c and the second is also between a-c. The two numbers should be adjacent

i means case insensitive g means unlimited number

When reg2 is changed to /a/ match, it will be returned as an array, and use str.length to print the number of occurrences of a

        var reg2 = /[a-c][a-c]/ig //Take out two bits, the first is between a and c, and the second is also
        var str2 = "bcdeAfgAaa666"
        var arr = str2.match(reg2) //Return the first value that matches, add g to return multiple
        console.log(arr);//bc Aa

Determine if it starts or ends with...

/^a/ Does it start with a /a$/ Does it end with $

Use the test function to judge

        var reg3 = /^a/i //a$ ends with a ^a starts with a
        var str3 = "abcdeAfgAaa666A"
        var arr1 = reg3.test(str3)
        console.log(arr1);

Finds that end with:

/\.(jpg|png)$/ /. means . (jpg|png---jpg or png $---ends with ..

        var reg4 = /\.(jpg|png)$/ //Find files ending in .jpg or .png
        var str4 = "qabAcdefAg6acbb66a.jpg"
        var re = str4.match(reg4)
        console.log(re);

one bit per character

[Zhao Qiancun][Cloud Crane][abc] Take one digit in each bracket and combine it

^[Zhao Qiancun][Cloud Crane][abc]Starting with a word in Zhao Qiancun

        var reg5 = /[Zhao Qiancun][Yunhe][abc]/g //Take one digit for each square bracket
        var str5="Zhao He a Zhao Yun bc Murazuru a"
        var arr3=str5.match(reg5)
        console.log(arr3);//'Zhao He a', 'Zhao Yun b', 'Mura Crane a']

Written question: remove trailing spaces

/(^\s+)|(\s+$)/g \s means space here means the beginning of a space or the end of a space

re=str.replace(reg,"") replace Replace the reg (starting space or trailing space) in the str character with ""null

        // Remove leading and trailing spaces from a string of written test questions
        // str.tirm()
        var reg=/(^\s+)|(\s+$)/g //remove trailing spaces
        var str=" abc  "
        var re=str.replace(reg,"")//remove spaces in str
        console.log(re);

/[a]+/ Multiple a

=/[a-b]+/ Multiple occurrences of a and b are fine

/a{3}/ Three connected together

Regular phone number

        var reg=/^1[3||5||7||8||9][0-9]{9}/ //1 starts with 35789 as the second digit followed by nine random numbers

        var str="18623481834"

        console.log(reg.test(str))

exec function

The nature and match are almost the same as returning the value that matches the regular expression, but the position of the regular expression of the string is opposite and the same as test

The second run will start looking after the value from the previous call

        var reg=/[a-z]{3}[1-7]/ig
        var str="ABC3ccc9bbb6"
        var re=reg.test(str)
        console.log(re);
        var re2=reg.exec(str)//straight back out
        var re3=reg.exec(str)//The second call will start looking after the value of the previous call
        console.log(re2);
        console.log(re3);

clone regular expression

reg.source represents a string in reg

var reg2=new RegExp(reg.source)

        var str="helloabc"
        var count=0
        var temp=0
        while(str.indexOf("lo",temp)!=-1){//Returns the position of the first occurrence starting at temp=0 and continuing if not equal to -1
                    count++
                    temp=str.indexOf("lo",temp)+1
        } 
        console.log(count);

Return to the first occurrence

re=str.indexOf("lo")

Determine the number of repetitions

str.indexOf("lo",temp)!=-1 indicates that the result is not equal to -1 and continues, which means that lo is matched to continue, no match means that the retrieval has been completed and return -1 while end

temp=0 means starting from the 0 subscript to detect the position where lo appears

Each loop temp is equal to the last matched position + 1

count is the number matched by the counter

        var str="helloabc"
        var count=0
        var temp=0
        while(str.indexOf("lo",temp)!=-1){//Returns the position of the first occurrence starting at temp=0 and continuing if not equal to -1
                    count++
                    temp=str.indexOf("lo",temp)+1
        } 
        console.log(count);