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Editorial Team
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Asked: 2026-05-29T19:30:08+00:00

In the following program when only the White Spaces are entered, it shows ex2

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In the following program when only the White Spaces are entered, it shows ex2 exception value less than 5, instead of showing ex4 exception This is not a valid number, I couldn’t understand the logic behind it. 

<html>
<head>
    <title></title>
    <script type="text/javascript">
        function promptCheck() {

            var val=prompt("Enter a Number between 5 and 10","");

            try {
             if(val=="") {
                 throw "ex1";
             }

             else if(val<5) {
                 throw "ex2";
             }

             else if(val>10) {
                 throw "ex3";
             }

             else if(isNaN(val)) {
                 throw "ex4";
             }
            }

            catch(err) {
                if(err=="ex1") {
                    alert("You have not entered any value");
                }
                 if(err=="ex2") {
                    alert("Value less than 5");
                }
                 if(err=="ex3") {
                    alert("Value greater than 10");
                }
                 if(err=="ex4") {
                    alert("This is not a valid number");
                }
            }

        }
    </script>
</head>

<body>
    <input type="button" value="Bring Mouse on Me!" onmouseover="promptCheck()" />
</body>
</html>
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1 Answer

  1. Editorial Team

    That happens because string with only whitespaces is treated as empty string and it it is converted to 0.

    So

    "    "*1 // => 0

    What you need to do is to parse value beforehand:

    var value = parseInt(val, 10); // would be NaN in case of empty string
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