ES6 new - string part

String extension

1.es6 New template string The quotation marks - ``

es6 Previous string shortcomings

New backquote benefits :

2.es6 New string instance method :

Static methods ( Non instance method ):

String instance method :

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String extension

1.es6 New template string The quotation marks - ``

es6 Previous string shortcomings

stay es6 Previously, the declared string used single quotation marks or double quotation marks , Disadvantages of single and double quotation marks :

(1) You can't change lines casually     (2)+ No. 1 splicing is cumbersome

New backquote benefits :

(1) Declare with a pair of backquotes : ` hello ` ; The backquote declaration type is also a string type

(2) Embed variables : You can embed any expression inside , grammar : ${ expression }

2.es6 New string instance method :

Static methods ( Non instance method ):

Constructor name . Method ( Parameters ) String.fromCharCode(10)

String instance method :

object / power . Method ( Parameters ) " aa ".split(" bb ")

Be careful : All instance methods of the string do not change the original string , Strings are read-only

(1)repeat(number) : Repeat the string a specified number of times and return , Round the decimal , Negative error str.repeat(2)

(2)startsWith(str,[startIndex = 0]) : Determine whether the string is a string start , Is to return true; no , return false

(3)endsWith(str,[endIndex = str.length - 1]) : Determine whether the string is a string ending , The optional parameter is subscript

(4)includes(str,[startIndex = 0]) : Determine whether a string contains a string , Include return true, Does not include return false

Can replace indexOf Method ,includes More semantically

(5)padStart(length,str) : String header padding , Returns the filled string , But it won't change the original string

(6)padEnd(length,str) : The end of the string is filled ,

length Represents the total length after filling ,length < str.length when , Will not do any filling , Returns the original string

(7)trimStart() : Remove the leading space of the string , Return the string after removing spaces

(8)trimEnd() : Remove the trailing space of the string  

trim() : Remove the leading and trailing spaces of the string

(9)repalceAll(searchValue | searchPattern,replacement): String global substitution

repalce(): Only the first search result will be replaced

Use in different situations :

(1) Both parameters are strings :console.log(str.replace("a","b")) console.log(str.replaceAll("a","b"))

(2) The first parameter is regular , The second parameter is the string : console.log(str.replace(/a/g,"b")) // Equivalent to global replacement

console.log(str.replaceAll(/a/g,"b")) //replaceAll Regular no /g Will report a mistake

(3) The first parameter is regular , The second parameter is callback :

const str = "ccbbaa" ;

const ret = str.replace(/a/g,function(matchStr,index,str){

console.log(mathStr,index,str); 

return " bb "        })  // Output : "a" 5 "ccbbaa" ; "a" 6 "ccbbaa" // Print twice

console.log(ret)

Callback function parameters : first : Strings that conform to regular rules ; the second : Subscript in the original character ; Third : The original character itself

In a string , Space is also a space !!