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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