String objects and methods in JavaScript

string object

Two kinds of creation of string object

var a="hello";

var b=new String("hello");

//The following is the method

//charAt() finds the characters in the string according to the subscript

　　 alert(a. charAt(3));//Return a certain character in the string based on the subscript

　　 alert(a.charAt(10));//Empty, the subscript cannot be found

//charCodeAt() returns the character at the specified position

var a="Hello world!Hello world!";

var d=" This is a string ";

alert(a.charCodeAt(1));//101

　　 alert(d.charCodeAt(3));// 26465

//String.fromCharCode() uses unicode encoding to return a string

　　 alert(String.fromCharCode(65,66,67 ));//

//concat() is used to connect one or more strings without changing the original array

var a="Hello world!Hello world !";

      var b="Purple smoke rises from the sunshine incense burner";

    var c="Not as good as Wang Lun to send me love";

      alert(a.concat(b ,c))

//search() finds the string to be matched. If found, returns the subscript of the first match. If not found, Return -1

　　　 var c="123456789";

　　 alert(c.search("567"));//4

　　 alert(c.search("5671"));//-1

　//replace() Use some words to replace other characters

　　 var d="Xiao Huang is a dog, Xiao Huang is very handsome";

　　 var e= d.replace("小黄","小黑");//Xiao Huang changes to Xiao Hei, only for the first time

　 var e=d.replace(/小黄/g,"小黑")//Everything in the string is changed

alert(e);

//split() Used to split a string into a string array, the original array remains unchanged

　　 var a="hello world!";

　　 alert(a.split(" "));

                                      alert(a.split(("o"));//hell, w,rld

                                                                                                                ()Returns the position where a specified character first appears in the string

　　var a="hello world!";

　　alert( a.indexOf("o"));//4

　　alert(a.indexOf("p"));//-1 No results were found -1

//lastIndexOf() searches from back to front



var a="hello world!";

 alert(a. lastIndexOf("o"));//7                                                                                                                                                                                 . ## 　　 alert('world')//If you find the first one, you will not find it 5

　　 alert(a.match(/world/g));//Regular expression (global search)

//slice() can extract a certain part of the string, which can be negative

　 var a="Hello world!Hello world!";

　 alert(a .slice(5,13));//The first subscript is required, not the second subscript

　　 alert(a.slice(-15,-7));

//substring() is the same as slice, but does not accept negative numbers

　 var a="Hello world!Hello world!";

　 alert (a.substring(4,12));

　 alert(a.substring(-3,-1));//Nothing

// substr() intercepts the specified number of characters starting from the specified subscript

　 var a="Hello world!Hello world!";

　 alert(a.substr(4,6)); //Truncate 6

starting from subscript 4 backwards

//toLowerCase() converts the string to lowercase

!";

            alert(a.toLowerCase()); !";

     alert(a.toUpperCase());

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