HTML-Files/Js.html at master · jaibhageria/HTML-Files · GitHub

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<html>
<!--script tag can appear anywhere in html-->
<!--preferably link external JS file because scripting in head will not act on tags defined inside body-->
<!--alert() is used to display a msg  as a pop-up-->
<!--prompt() is used to ask a question  Use , "" to specify default value it will return the value typed in-->
<!--confirm() gets a yes or no answer from the user-->
<!--variables

interpreter assumes the type of the variable depending on its value
JS is a dynamically typed langage
JS is a weakly typed language because the value given to a variable ca
use 'var' to declare a variable
datatypes=number,string,boolean,null,undefined are primitive datatypes
there is no differentiation for numbers....all decimals,integers,floats etc. are all treated as numbers under the same umbrella
all numbers are stored in 64bit IEEE format


-->
<!--
operators in JS:
Arithmetic:+,-
Increment/Decrement
Assignment
Bitwise:^(XOR),|(OR),&(AND),>>(right shift is like divide by 2),<<(left shift is multiply by 2)
Logical
Relational: ===(strictly equal to), !==(strictly not equal)


-->
<head>
<title>JS1</title>
<style></style>
<script>
     alert("Hello, World!");
     var a=10;
     b=20;//both the above ways of declarations are correct but there is a slight difference
     alert(typeof c);//returns type as undefined because c is not defined anywhere in the program
     var c;//still type will be undefined until it is initialised
     b = null;//typeof is object    null is intentional by user and undefined is by the engine(unintentionally)
     var num = parseInt(prompt("Enter a number"));
     document.write(num);
     var color = prompt("Enter a Color : ");
     switch(color){
       case "Red":
          document.write("<style> body{background-color:red;} </style>");
          case "Blue":
             document.write("<style> body{background-color:blue;} </style>");
             case "Green":
                document.write("<style> body{background-color:green;} </style>");
     }
</script>
</head>(
<body>
  <script>
    name = prompt("What is your Name?","name")
    if(name=="null")
    {
      alert("EXITING");
    }
    else{
     document.write(name)//used to print on html
     document.write("<h1 style=\"text-align:center   \">"+name+"</h1>");


     confirm("Are you sure your name is "+name+" ?")
     x='I am good';
     y="I am better";//both variables are string types single or double qoute are same
     alert(typeof x);
     alert(typeof y);
     a=true;
     alert(typeof a);
   }
  </script>
  <script src="P1.js"></script>
</body>
</html>