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Content of string
2022-07-07 08:01:00 【Code machine - Ying】
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] );
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