Summary of JavaScript string methods

Single quotation marks inside the string can use double quotes, double quotation string inside can also use single quotation marks

"Hello ' world '" ' Welcome "to" JS "

Second, multirow and escape

If you want to use single quotation marks (or double quotes inside a double-quoted string) inside a single-quote string, you must precede the inner single quotation mark (or double quotation mark) with a backslash to escape.

var str = "Did you \" love\ "Me"var str = ' Do you \ ' love\ ' me '

The string default can only be written in one line, the number of lines will be error.

'ABC'//  syntaxerror:unexpected token illegal

The above code divides a string into three lines, and JavaScript will error

Method One: If the long string must be divided into multiple lines, you can use a backslash at the end of each line.

var str = "welcome come to\     Chongqing.welcome to    Chongqing"

The above code indicates that, after adding a backslash, the original string written on a line, can be divided into multiple lines, the effect is exactly the same as writing in the same line. Note that the backslash must be followed by a newline character, not other characters (such as spaces), or it will be an error.

Method Two: The Join operator ( + ) can concatenate multiple single-line strings to simulate a multiline string.

var str = "Welcome come to" +    "chongqing.welcome to" +    "Chongqing"

Third, length calculation str.length

var str = "Hello"; Console.log (str.length); // 5

Four, string interception

1, substr (A, b) the first parameter is the starting position, the second parameter is the length of the Intercept

var str = "Welcome to JavaScript"Console.log (Str.substr (1,3))//ELC

2, substring (A, b) the first parameter is the starting position, the second parameter is the end position, the interval is [a, b]

var str = "Welcome to JavaScript"Console.log (str.substring (1,3))//el

3, Slice (A, B) ibid.

Five, string split into an array split (?)

var str = "We lc ome"console.log (Str.split (""))//["We", "LC", "ome"]

Six, query substring

1, indexOf (?) starts from the beginning of the string, finds the corresponding coordinates and exits, cannot find return-1 and exits ( does not support regular )

var str = "We lc ome"console.log (Str.indexof ("E"))//1

2, lastIndexOf (?) Search from the end of the string, find the corresponding coordinates returned and exit, cannot find return 1 and exit ( not supported )

var str = "We lc ome"console.log (Str.lastindexof ("E"))//8

Seven, string matching

1. Match (?) the function is called on a string and accepts a parameter (which can be a regular ).返回匹配的数组，否则返回null

var str = "Hello my World"; var s3 = Str.match (/o/g); Console.log (S3)//["O", "O"] 

2, search (?) is similar to indexof (), find a matching string to return the corresponding coordinates, cannot find return-1, the difference is that search can use regular expressions, indexof cannot use regular expressions, If you are looking for a string with some characteristics (such as looking for a string that starts with an L and followed by a number), then indexof () has nothing to do with the regular expression and the search () method.

var str = "Hello my World"; var s1 = str.search (/o/g);   Console.log (S1)//4

The trim () method is used to remove spaces before and after a string

var str= "   Hello World   "; Console.log (Str.trim ()); //

Nine, replace (A, B) method, the first parameter is the string to be replaced, the second argument is a replacement string (the first argument is a character, only the most recent replacement, the first parameter if it is a regular, you can find and replace all the matching string)

The first argument is a string
var str = "Hello my World";     var s2 = str.replace (' o ', ' your ');    Console.log (S2)//hellyour My World
The first parameter is a regular form
var str = "Hello my World";
var s2 = str.replace (/o/g, ' your ');
Console.log (S2)//hellyour my Wyourrld

X. Uppercase and lowercase conversions

var str = "Hello";    Str.touppercase (); // HELLO    Str.tolowercase (); // Hello

Summary of JavaScript string methods