JavaScript Language Basics

the basic syntax of JS

  /*Multi-line comments **/        //single-line comment//variable assignment defaults to a newline character as a terminator with a semicolon as the ending symbol        vari; I=10; S= "Hello"; varb=true; Console.log (i,typeofi);//Number typeConsole.log (s),typeofs);//String TypeConsole.log (b,typeofb);//Boolean type        //define an array        vararr=[11,222, "Hello"]; Console.log (arr,typeofarr); //Undefined type        varabc//1 Declaration unassigned, Get undefined 2 function no return valuealert (ABC); Alert (typeofabc

operator

// calculation operator: +-*/%  + +--      var i=0;      I+=1;    // i=i+1      ret=i++;     // i=i+1  First assigns the value to calculate the ret=++i again      ;       // i=i+1  Calculate the re-assignment first  // = = = All equals      Console.log ("1" ==1)   // true     Console.log ("1" ===1)   //  false

String Object

    //How to create:       vars=NewString ("Hello"); varS2= "Hello2"; //Properties and Methods        vars= "Hello World";        Console.log (s.length);        Console.log (S.touppercase ()); Console.log (S.charat (3));//get characters by indexConsole.log (S.indexof ("w"));//get an index by characterConsole.log (S.substr (1,3));//string truncation, substr (starting position, truncated length)Console.log (s.substring (1,3));//string truncation, substr (starting position, truncated position)Console.log (S.slice (1,3));//string truncation, substr (starting position, truncated position)        varRet=s.split ("");//slicingConsole.log (ret)

Array Object

    //creating an Array object        vararr=[111,222,333]; varArr2=NewArray (111,222,333);        Console.log (Arr.tolocalestring ()); Console.log (typeofarr.tolocalestring ()); //Array Method        vararr=[11,223,34, "Hello",true]; Console.log (arr[3]); //Join Method        varRet=arr.join (""); Console.log (ret);//Reverse Reverse Sort sort        vars=[100,23,44,12]; functionmysort (x, y) {returnX-y} console.log (S.reverse ()); //[ +,--]Console.log (S.sort (Mysort));//[A. , Max.]//push adds a value pop delete        vararr=[11,22,33]; Arr.push (45,67);        Console.log (arr);        Console.log (Arr.pop ()); Console.log (arr);

Function Object

// Definition of a         function        function function name () {           function body         }        //  anonymous function        ( function () {            Functional body        } )();

JavaScript Language Basics