Content of string

One , Loop operation of string

Loop traversal method of string :

for loop

for....in loop

for....of loop

Two , String query

   1    character string .indexOf()    Regular expressions are not supported

        character string .search()      regular expression

Query whether there are matching characters in the string

      If there is an index subscript that returns the first occurrence

      If there is no return -1

    2    character string .lastIndexOf();

  Query whether there are matching characters in the string

        If there is an index subscript that returns the last occurrence

        If there is no return -1

var str = ' How big is the big mouth monkey ';

        //  Inquire about  
        console.log( str.indexOf( ' Big ' ) );
        console.log( str.search( ' Big ' ) );


        console.log( str.lastIndexOf( ' Big ' ) );

    

 

  3、 ... and       String truncation

1    character string .substr( Parameters 1, Parameters 2)

          Parameters 1    The starting position of the intercepted string

                  0 Or a positive number         Index subscript of starting position

                  negative                   Intercept from the penultimate character to the last bit of the string

          Parameters 2      Number of intercepted strings

                If no parameters are set 2  Intercept to the end of the string

                  Set the number of intercepted characters

2    character string .substring( Parameters 1, Parameters 2)

          Parameters 1        Intercepted string   The starting position

                0 Or a positive number         Index subscript of starting position

                negative                 Intercept from the first character

        Parameters 2            The end position of the intercepted string

              0 Or a positive number             The interception result does not contain the end position

              negative                       Intercept to the beginning of the string

//  from   The index subscript is 3 Start with the fourth character of   Intercept to   The last bit of the string 
        var res1 = str.substr( 3 );
        console.log( res1 );

        //  from   The penultimate character begins   Intercept to   The last bit of the string 
        var res2 = str.substr( -3 );
        console.log( res2 );

        //  from   The index subscript is 3 Start with the fourth character of   Intercept  4 Characters 
        var res3 = str.substr( 3 , 4 );
        console.log( res3 );

        //  from   The penultimate character begins   Intercept   Intercept 2 Characters 
        var res4 = str.substr( -3 , 2 );
        console.log( res4 );


        // substring Intercepting string 

        //  The subscript from the index is 3 Start with the fourth character of   Intercept to   Last bit of string 
        var res5 = str.substring( 3 );
        console.log( res5 );

        //  Parameters 1  Cannot be set to a negative number   Intercept from the beginning of the string 
        // var res6 = str.substring( -3 );
        // console.log( res6 );

        //  from   Index subscript   yes  3 Start intercepting the position of  
        //  Intercept to   The index subscript is  10 The location of  
        //  however   result   barring   The index subscript is  10 The location of 
        var res7 = str.substring( 3 , 10 );
        console.log( res7 );


        var res8 = str.substring( 3 , -5 );
        console.log( res8 );

Four       String case is unified

character string .toLowerCase()

          All characters are lowercase

character string .toUpperCase()

        Capitalize all characters

        var str = 'abCdEfGh' ;
        console.log(str.toLowerCase())
        //  All characters are lowercase 
        console.log(str.toUpperCase())
        //  Capitalize all characters 
        

 

5、 ... and     Get character function

    character string .charAt()

          Get characters according to index subscript

  character string .charCodeAt()

          Get the characters according to the index subscript ASCII Code number

var str = 'abcedfg' ;

        console.log( str.charAt( 1 ) );
        console.log( str.charCodeAt( 1 ) );
        console.log( str[1] );