JS string method summary

I have summarized that it can be used as a query manual
The following two strings are explored , All string methods do not change the original string

let str = '3311 Method collation of strings 1122'
let str1 = ' character string 1'

indexOf(str,startIndex)

Returns the subscript of the position where the formal parameter appears in the caller , Returns if it does not exist -1, The second parameter is to search from the taxi index

// ①indexOf(str,startIndex) 
        //result==>12 '3311 Method collation of strings 1122'
        console.log(str.indexOf(1,5)+'\t'+str)

charAt(index)

Returns the character at the specified index position

  //result==> word  3311 Method collation of strings 1122
        console.log(str.charAt(4)+'\t'+str)

concat(…args)

Combine multiple characters with the caller to form a new string .！！ This method does not change the original string ！！

//result==>3311 Method collation of strings 1122 character string 1 3311 Method collation of strings 1122 
        console.log(str.concat(str1)+'\t'+str)

substring(startIndex,endIndex?)

This method intercepts the string from the specified start index position to the specified end index position , Pay attention to closing on the left and opening on the right , If you do not pass the second parameter, you will intercept from the specified index to the end of the string ( The starting index position can be negative , A negative number represents the reverse from the back to the front startIndex individual ) ！！ This method does not change the original string ！！

 //result==> Method collation of strings 1122 3311 Method collation of strings 1122
        console.log(str.substring(4)+'\t'+str)
        //result==> Method collation of strings 
        console.log(str.substring(4,12))

substr(startIndex,length)

This method intercepts the number of strings starting from the specified index position as the second parameter ( The starting index position can be negative , A negative number represents the reverse from the back to the front startIndex individual )！！ This method does not change the original string ！！

 //result==> A string of  3311 Method collation of strings 1122 
        console.log(str.substr(4,4)+'\t'+str)

slice(startIndex,endIndex?)

This method intercepts part of the string from startIndex-endIndex Left closed right away If the second parameter is negative , The character from the specified position to the end of the number from the back to the front will be extracted . If the first argument is negative , There is no output , No mistake. . ！！ This method does not change the original string ！！

//result==> Method collation of strings  
        console.log(str.slice(4,12)+'\t'+str)

replace( Parameters 1： Regular / character string , Parameters 2： New string / function )

//result==>3391 Method collation of strings 1122
        console.log(str.replace('1','9'))
        //result==>aaaa Method collation of strings aaaa  You can use g Realization replaceAll The effect of 
        console.log(str.replace(/\d/g,'a'),str)
        //result==>1111 Method collation of strings 1111  If the second argument is a function , Will replace the parameter with the return value of the function 1  This function takes four arguments （ Parameters a: Represents the matching parameter 1 Which ones are here a:3,3,1,1,1,1,2,2  Parameters b: On behalf of the parameter a Those subscripts of   Parameters c： On behalf of the caller itself, here is str）
        console.log(str.replace(/\d/g,(a,b,c)=>1))

replaceAll()

Don't introduce too much replace, The only difference is ,replaceAll All matches will be replaced directly ！！ This method does not change the original string ！！

split(str,num?)

Use the specified separator string to place a Str Object is divided into substring arrays , The second parameter determines how many ！！ This method does not change the original string ！！

//result==> ['3', '3', '1', '1', ' word ', ' operator ', ' strand ', ' Of ', ' Fang ', ' Law ', ' whole ', ' The reason is ', '1', '1', '2', '2']
        console.log(str.split(''))
        //result==>['3', '3']
        console.log(str.split('',2),str)

trim()

Remove white characters at both ends of empty string , The middle space cannot be removed , You can remove all spaces through the above replace Method ,\s Regular table blank characters

//result==>a a a
        let trimStr = ' a a a '
        console.log(trimStr.trim())
        //result==>aaa
        console.log(trimStr.replace(/\s/g,''))

match(str)

Return results 1 It returns an array , The array contains the result information of string matching regular expression . Return results 2 If the global match , The matching result will be returned as an array

//result==>[' character string ', index: 4, input: '3311 Method collation of strings 1122', groups: undefined] index It refers to the index that matches the successful start position , Input  Property contains the entire string being searched  　　groups： An array of capture groups or  undefined（ If no named capture group is defined ）
        console.log(str.match(' character string ')) 
        //result==> ['3', '3', '1', '1', '1', '1', '2', '2']
        console.log(str.match(/\d/g))```