Question

171

javascript : checking boolean values

rated 0 times [ 176] [ 5] / answers: 1 / hits: 46679 / 13 Years ago, wed, april 27, 2011, 12:00:00

I have a boolean value set as a hidden variable in the form and I have the below javascript .

         $().ready(function() {



             var flag =  $('#popUpFlag').val();



             alert(flag = +flag);



             if(flag){

                alert(flag is true);

             }else{

                alert(flag is false);

             }

        })

These are the outputs for the alert .

         flag =

         flag is false





         flag = false

         flag is false





         flag = true

         flag is false

My concern is obviously the third output . When the flag is true , why is it printing flag is false , instead of flag is true . I tested it in IE8 and FF 4

Suggestions are welcome.

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anabeldaliad

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2 Years ago

answered 13 Years ago reed · Accepted Answer

No, you don't have a boolean value in the hidden field. The value in the field is always a string.

When you use the string value as if it was a boolean value, you get unexpected results. A condition is false if the value is false, 0, or null, but the string false is neither, so it's evaluated as true.

If you want a boolean value, you have to parse the string. An easy way is to simply check if the string has a specific value:

var flag =  $('#popUpFlag').val() === 'true';