javascriptBasic/01_index.html at master · YoungjuneKim/javascriptBasic · GitHub

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<!DOCTYPE html>
<html lang="ko">
<head>
    <meta charset="UTF-8">
    <title>HTML Intro Test</title>
</head>

<script>
    //Boolean, Number, String, Array, Object 5가지타입
    var b = new Boolean(true); // var b = true ;
    var n = new Number(3);  //var n = 3 ;
    var s = new String("hello javascript world"); //var s ="hello" or var s = 'hello' ;
    var arr = new Array();  //var arr =[] ;
    var obj = new Object(); //var obj ={} ;

    //alert('hello javascript world!!') ;
    var a ="heoll javascript world"; // = new String("heoll javascript world")
    var x =new Number(3)
    var y = 4 ; //var y =new Number(4)
    //alert('x+y:'+ x+y) ;
    alert(x+y) ;

    var z ;
    z=3 ; //이걸빼면 undefined
    alert(typeof z)  ;
    alert(z) ; //undefined

    //if(z=="undefined") -- error
    //if(z==undefined) -- ok

</script>

<body>
    <h1>여러분을 환영합니다!!</h1>
</body>
</html>