Detailed explanation of strings in JavaScript

This article mainly shares with you the detailed explanation of strings in JavaScript, hoping to help everyone.

1. Basics of strings

1. Creation of strings

Basic data types String
var str = "string";

Referenced data type String
var strObj = new String("string");

2. Common attributes

length String length

var arr="abc"; console.log(arr.length)

3. Commonly used methods

eg: var s = "see me fly I am singing in the sky";

①charAt() returns the character at the specified position in the string

Gets the specified character based on the index, the effect is equivalent to s[1]

console.log(s.charAt(1) );//e

②concat can be used to connect two or more strings and has the same effect as +

console.log(s.concat(" !"," 00")) //see me fly I am singing in the sky ! 00

③indexOf();
a. indexOf() checks whether a string contains the specified content
——If it contains the content , the index
of its first occurrence will be returned - if the specified content is not found, -1

b. indexOf('specified character', index a); starts from the position of a Search for the specified character

console.log(s.indexOf("b")); //If not found, return -1
console.log(s.indexOf("m")) ; //4
                        console.log(s.indexOf("s",5)); //16

④lastIndexOf(); The usage is the same as IndexOf

——only However, IndexOf() searches from the front, while lastIndexOf() searches from the back to the top, but the index still starts from 0

console.log(s.lastIndexOf("s")); //31
            console.log(s.lastIndexOf("s",5)); //Look forward starting from index 5, 0

⑤slice(start,end) intercept the specified content from the string, Does not affect the original string, just returns the intercepted specified content

——start is the starting position (including), end is the end index (excluding the end character)

— —If there is no end, the characters from start to the end will be intercepted

- You can also pass a negative number, and the calculation will start from the end instead of from the beginning

console.log(s.slice(1,5)); //ee m
            //a.要 截取 “I am singing”
            console.log(s.slice(s.indexOf("I"),s.lastIndexOf("g")+1))//I am singing
            //b.要 截取 “in the sky”
            console.log(s.lastIndexOf("i"))
            console.log(s.slice(-10))//in the sky
            //注意：数组都是从前安排到后面的，所以从末尾-1开始数，i为-10，所以（-10,-1)
            //但是由于-1这个位置表示到这个数值之前，就停止了，这个数值不进来，所以可以去掉

⑥substring( start, stop) intercepts a string, similar to slice()
——subString(start,stop);start starts (including), stop ends (exclusive)
——This method cannot accept negative values ​​​​as Parameters, if a negative value is passed, the default is 0
——Automatically adjust the position, if the stop parameter is less than start, it will be automatically exchanged

var newarr2='see me fly ';
            console.log(newarr2.length)
        	console.log(s.substring(11,26)); //I am singing in
            console.log(s.substring(10,1)); //ee me fly

⑦substr(start,length) intercepts the string
——start starts (Inclusive), length is the intercepted length

//To intercept "I am singing"
var newarr='I am singing';
console.log(s.substr(s.indexOf ("I"),newarr.length));

⑧split(separator) method is used to split a string into a string array

——separator string or regular Expression

                                                                                                                                                                to be split between each character of split(""), and split(" ") to split the string based on spaces.  

console.log (s.split(" ")); //["see", "me", "fly", "I", "am", "singing", "in", "the", "sky"]

⑨ The toLowerCase() method is used to convert strings to lowercase.
The toUpperCase() method is used to convert the string to uppercase

console.log(s.toLowerCase());//see me fly i am singing in the sky
console.log( s.toUpperCase());//SEE ME FLY I AM SINGING IN THE SKY

⑩replace(old,new)replace string
----old is the character of the original string, new is New

---Replace the first occurrence of

console.log(s.replace('me','you'));//see you fly I am singing in the sky

Related recommendations:

js implements repeated splicing of multiple strings from beginning to end

javascript implements inverted strings Method

Summary of JavaScript string methods

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