JS string method Encyclopedia

One 、ES5 String method

（ One ） Method of adding special effects

• length： attribute , Returns the length of the string

var str="abcde"
console.log(str.length)  //5

• anchor()     establish HTML anchor

var str=" use Baidu Search "
re=str.anchor("http://www.baidu.com")
console.log(re)    //<a name="http://www.baidu.com"> use Baidu Search </a>

• link()   Display the string as a link

var str="Hello World"
re=str.link("http://www.baidu.com")	
console.log(re)   //<a href="http://www.baidu.com">Hello World</a>

• big()   Display strings in large font

var str="Hello World"
var re=str.big()
console.log(re)  //<big>Hello World</big>

• small() Use small font size to display strings

var str="Hello World"
var re=str.small()
console.log(re)  //<small>Hello World</small>

• blink() Show flashing string

var str="Hello World"
var re=str.blink()
console.log(re)   //<blink>Hello World</blink>

• bold()   Use bold to display strings

var str="Hello World"
var re=str.bold()
console.log(re)   //<bold>Hello World</bold>

• sub()   Display a string as a subscript

var str="Hello World"
var re=str.sub()
console.log(re)  //<sub>Hello World</sub>

• sup()   Display the string as superscript

var str="Hello World"
var re=str.sup()
console.log(re)  //<sup>Hello World</sup>

•  fontcolor() Use the specified color to display the string

var str="Hello World"
var re=str.fontcolor("red")
console.log(re)  //<font color="red">Hello World</font>

• fontsize()   Use the specified size to display the string

var str="Hello World"
var re=str.fontsize("30px")
console.log(re)  //<font size="30px">Hello World</font>

•  italics()   Use italics to display strings

var str="Hello World"
var re=str.italics()
console.log(re)  //<i>Hello World</i>

 （ Two ） String conversion

•  toLocaleLowerCase() Convert string to lowercase

var str="Hello World"
var str1=str.toLocaleLowerCase();
console.log(str); //Hello World
console.log(str1); //hello world

• toLocaleUpperCase() Convert strings to uppercase

var str="Hello World"
var str1=str.toLocaleUpperCase();
console.log(str); //Hello World
console.log(str1); //HELLO WORLD

• toLowerCase()   Convert string to lowercase

var str="Hello World";
var str1=str.toLowerCase();
console.log(str); //Hello World
console.log(str1); //hello world

• toUpperCase()   Convert strings to uppercase

var str="Hello World";
var str1=str.toUpperCase();
console.log(str); //Hello World
console.log(str1); //HELLO WORLD

•  toString()   Return string

var num=100;
var str=num.toString();    
console.log(str)  //"100"

（ 3、 ... and ） Common methods  

•  charAt()     Returns the character at the specified subscript position   if index be not in [0,str.length) Between, an empty string is returned

var str="hello world";
var str1=str.charAt(6);
console.log(str1); // w    Subscript from 0 Start   The space is also called 

• charCodeAt()     Returns the value of the character at the specified position Unicode code   The return value is 0 - 65535 Integer between

var str="hello world";
var str1=str.charCodeAt(1);
var str2=str.charCodeAt(-1); 
console.log(str1); //101
console.log(str2); //NaN

• concat()     Connect the string and return a new string   The original string is not changed

var str = "Hello";
var str1 = "World";
var str2 = str.concat("~",str1);// ==>"Hello" + "~" + "World";
console.log(str2)   //"Hello~World"

• indexOf()   Retrieving a string returns the subscript of the first occurrence of the specified substring in the string Return if not found -1

//  Find the range  [0,string.length - 1)
var str="Hello World";
var str1=str.indexOf("o");
var str2=str.indexOf("world");
var str3=str.indexOf("o",str1+1);
console.log(str1); //4  By default, only the first keyword position is found   From the subscript 0 Start looking for 
console.log(str2); //-1  Case sensitive   No return found -1
console.log(str3); //7   The second parameter represents the subscript of the starting position 

• lastIndexOf()   Search the string from back to front and return the subscript of the last position of a specified substring in the string

var str="Hello World";
var str1=str.lastIndexOf("o");
var str2=str.lastIndexOf("world");
var str3=str.lastIndexOf("o",str1-1);
console.log(str1); //7
console.log(str2); //-1   Case sensitive   No return found -1
console.log(str3); //4   The second parameter indicates which subscript to start from , If it is not written, it will start from the last character by default 

• match() Match one or more regular expressions and return an array of all the searched keyword contents

var str="Can you can a can as a canner can a can?";
var reg=/can/ig;
var str1=str.match(reg);
console.log(str1); //['Can', 'can', 'can', 'can', 'can', 'can']
console.log(str.match("Hello")); //null

• replace()    Replace some characters with others Or replace a substring that matches a regular expression

var str="Hello World";
var reg=/o/ig; //o For the keyword to be replaced , Cannot quote , Otherwise, the replacement will not take effect ,i Ignore case ,g Represents a global lookup .
var str1=str.replace(reg,"**")
console.log(str1); //Hell** W**rld    Case sensitive 

• replaceAll()   Replace some characters with others in the string Or replace all substrings that match the regular expression

var str = "Hello";
var str1 = str.replaceAll("l", "o");
console.log(str1); //Heooo

• search()     Retrieve the value that matches the regular expression If the search is successful, the matching index value in the string will be returned. Otherwise, it will return -1

var str = "Hello World";
var str1 = str.search("hi");
console.log(str1) // -1

• trim()  Remove spaces at both ends of the string

var str = "   Hello World!        ";
console.log(str.trim()); // Hello World!

（ Two ） Intercept part of string

• split() Split a string into an array of strings   Return a new array

var str="h e l l o";
var str1=str.split("");// Use an empty string as a delimiter , Every character of the string is divided 
var str2=str.split(" "); // Use the space as the separator 
var str3=str.split("",4); // The second parameter specifies the maximum length of the returned array 
var string="1:2:3";
var str4=string.split(":");
console.log(str1); // ['h', ' ', 'e', ' ', 'l', ' ', 'l', ' ', 'o']
console.log(str2); // ['h', 'e', 'l', 'l', 'o']
console.log(str3); // ['h', ' ', 'e', ' ']
console.log(str4); // ['1', '2', '3']

• substr()     Extract the characters of the specified length in the string from the starting index number

//substr(start, length)  
var str="Hello World";
var str1=str.substr(1)
var str2=str.substr(1,3);
var str3=str.substr(-3,2);
console.log(str1); //ello World 
console.log(str2); //ell
console.log(str3); //rl

• substring() Extract the character between two specified index marks in the string

//substring(start, end)    Range [start, end)
var str="Hello World";
var str1=str.substring(2)
var str2=str.substring(2,2);
var str3=str.substring(2,7);
console.log(str1); //llo World
console.log(str2); // If two parameters are equal , Return length is 0 The empty string of 
console.log(str3); //llo W

• slice() Extract a fragment of a string , And return the extracted part in the new string

//slice(start, end)   Range [start, end)  When start>end  Returns an empty string 
var str="Hello World";
var str1=str.slice(2); // If there is only one parameter , Then extract all strings from the beginning subscript to the end 
var str2=str.slice(2,7); // Two parameters , The extraction subscript is 2, To the subscript 7 But it doesn't include the subscript 7 String 
var str3=str.slice(-7,-2); // If it's a negative number ,-1 Is the last character of the string   Extraction range is [-7,-2) String 
console.log(str1); //llo World
console.log(str2); //llo W
console.log(str3); //o Wor

Two 、es6 New string method

（ One ） Identification of substrings

• includes()： Returns a Boolean value , Determine if the parameter string is found .

var str = "hello"
var re = str.includes("o")
console.log(re) //true

• startsWith()： Returns a Boolean value , Judge whether the parameter string is in the head of the original string .

var str = "hello"
var re = str.endsWith("h")
console.log(re) //false

• endsWith()： Returns a Boolean value , Judge whether the parameter string is at the end of the original string .

var str = "hello"
var re = str.startsWith("h")
console.log(re) //true

Be careful ：

• These three methods only return Boolean values , To know the position of the substring , Still have to use indexOf and lastIndexOf 

• If these three methods pass in regular expressions instead of strings , Will throw an error

•  IndexOf and lastIndexOf Will convert the regular expression to a string and search it

• All three methods support the second parameter , Indicates where to start the search

（ Two ） String filling （ completion ）

• padStart： Returns a new string , Represents a parameter string from the header （ left ） Complete the original string

var str = "100000"
var re = str.padStart(11, "6666")
console.log(re) //66666100000

• padEnd： Returns a new string , Indicates that a parameter string is used from the end （ On the right side ） Complete the original string

var str = "100000"
var re = str.padEnd(11, "6666")
console.log(re) //10000066666

• Two parameters ： The first parameter is to specify the minimum length of the generated string , The second parameter is the string used to complete . If the second parameter is not specified , Fill with space by default
• If the specified length is less than or equal to the length of the original string , Return the original string
• If the length of the original string plus the completion string is greater than the specified length , The completion string that exceeds the number of digits is truncated

（ 3、 ... and ） Duplicate string  

• repeat()： Returns a new string , Indicates that the string is repeated a specified number of times and then returned

var str = "hello"
console.log(str.repeat(2))  //hellohello

• If the parameter is a decimal , Rounding down
• If the parameter is 0 to -1 Decimal between , You will get -0 , Equate to repeat 0 Time
• If the parameter is NaN, Equate to repeat 0 Time
• If the parameter is negative or Infinity , Will report a mistake
• If the parameter passed in is a string , The string is first converted to a number

（ Four ） Template string

• The template string is equivalent to the enhanced version of the string , Use back quotes `
• Except as a normal string , It can also be used to define multiline strings , You can also add variables and expressions to a string
• The variable name is written in ${} in ,${} You can put JavaScript expression

// Wrap splice 
        var a = 123
        var str = `hello${a}
        h5
        `
        console.log(str)  /*  hello123
                          h5
        
                          */
        var r = parseInt(Math.random() * 225)
        var g = parseInt(Math.random() * 225)
        var b = parseInt(Math.random() * 225)
        var rgb = 'rgb(' + r + ',' + g + ',' + b + ')'
        var rgb2 = `rgb(${r},${g},${b})`
        console.log(rgb)    //rgb(156,61,50)
        console.log(rgb2)   //rgb(156,61,50)

• Example

var str1="hello"
var r=200
var str2=`<div
	style="color:rbg(${r},100,100)">${str1}<div>`
console.log(str2)  /*<div
			       style="color:rbg(200,100,100)">hello<div>
                   */