Es6--string (string)

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1. Identification of substrings

        （1）includes( )

        （2）startsWith( )、endWith( )

        （3）repeat( )

 2.padEnd( )、padStart( ): String completion

 3. Template string

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1. Identification of substrings

ES6 Before judging whether the string contains substrings , use indexOf Method ,ES6 A new method for identifying substrings is added

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

• startsWith()： Returns a Boolean value , Judgment parameter string Whether it is at the head of the original string .

• endsWith()： Returns a Boolean value , Judgment parameter string Whether it is at the end of the original string .

（1）includes( )

	        String.prototype.mytool=function(){			
	
			}
			var str="hello"
			var re=str.fontcolor("red")

	        var str="hello, Huaqing vision "
			console.log(String.prototype)
			var re1=str.includes(" Huaqing ")
			var re2=str.includes(" ")
			var re3=str.includes("")
			console.log(re)

Running results ：

 

（2）startsWith( )、endWith( )

        startsWith( 81,1): The positive number of the second parameter means the first one from front to back

	        var str="182828323410"
			var str2=str.startsWith("81",1)
			var str3=str.endsWith("2341",11)
			console.log(str2,str3)

Running results ：

（3）repeat( )

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

        repeat( ): There are no numbers in it , Output space

        repeat( Numbers ): What is the number , Repeat several times

for example 1：

	        var  str=" Huaqing vision "
			var  str2=str.repeat(2)
			console.log(str2)

Running results ：

 

for example 2： All the elements in the number are used * Instead of

	        var  str=" Huaqing vision 666"
			var  str2="*".repeat(str.length)
			console.log(str2)

Running results ：

 2.padEnd( )、padStart( ): String completion

        It doesn't change the original array

• padStart： Returns a new string , Parameter string for Complete the original string from the head .

• padEnd： Returns a new string , Parameter string for Complete the original string from the tail .

The above two methods accept two parameters , The first parameter Is the specified build The minimum length of the string , The second parameter It's for Completed string . If The second parameter was not specified , Fill with space by default .

for example ：

	        var str="99"
			var str2=str.padEnd(6,"abc")
			var str3=str.padStart(6,"abc")
			console.log(str2,str3)

Running results ：

 3. Template string

The template string is equivalent to the enhanced version of the string , Use back quotes `, Except as a normal string , just so so Used to define multiline strings , You can also add variables and expressions to a string

  Running results ：