How do I evaulate a string value as a boolean in javascript / jQuery?

Question

I have an asp.net webform with a textbox. The value of the textbox is "False" and has been verified by viewing the page source in the browser.

Despite being set to false the following code results in beginDateReqd being set to false and consequently, DateParms being displayed when it shouldn't be.

var beginDateReqd = Boolean($('.HiddenBeginDateTimeRequired').val());
if (beginDateReqd) {
    $('.DateParms').show();
}

What am I doing wrong? Thanks!

Please check this existing question for more details. stackoverflow.com/questions/263965/… — Saurabh Sharma
– Saurabh Sharma, Commented Nov 15, 2011 at 19:38

Blazemonger · Accepted Answer · 2011-11-15 20:22:11Z

2

Safer would be first to convert value "toLowerCase" and then compare with "true" value:

var beginDateReqd = ($('.HiddenBeginDateTimeRequired').val().toLowerCase() == "true");
if (beginDateReqd) {
    $('.DateParms').show();
}

edited Nov 15, 2011 at 20:22

Blazemonger

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answered Nov 15, 2011 at 19:31

Tomasz Mikuś

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Comments

Polynomial · Accepted Answer · 2011-11-15 19:24:53Z

1

Why not just use a comparison operator?

var beginDateReqd = ($('.HiddenBeginDateTimeRequired').val() == "True");
if (beginDateReqd) {
    $('.DateParms').show();
}

answered Nov 15, 2011 at 19:24

Polynomial

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Comments

Royi Namir · Accepted Answer · 2011-11-15 19:25:09Z

1

    var beginDateReqd = parseBoolean ($('.HiddenBeginDateTimeRequired').val());
    if ( beginDateReqd  ) {
        $('.DateParms').show();
    }



function parseBoolean(str) {
  return /^true$/i.test(str);
}

answered Nov 15, 2011 at 19:25

Royi Namir

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3 Comments

gilly3 Over a year ago

Pardon my nitpick, but I'd either rename that function isTrue() or throw an error if the value is not either true or false.

Polynomial Over a year ago

Using regex for this is like going after a fly with a tactical nuclear strike... what's wrong with just foo == "True"?

gilly3 Over a year ago

@Polynomial - Do regular expressions perform worse than string comparison? Can you point me to an article on the subject? Personally, I like them - they are so much more precise and meaningful than doing eg mystring.toLowerCase() == somestring.

Ben · Accepted Answer · 2011-11-15 19:30:31Z

0

The Boolean object does not parse string values for truthiness. You should be using a comparison operator or a regex test. See http://www.w3schools.com/js/js_obj_boolean.asp

answered Nov 15, 2011 at 19:30

Ben

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Comments

amit_g · Accepted Answer · 2011-11-15 19:31:12Z

0

Use comparison after making sure of the case

var beginDateReqd = ($('.HiddenBeginDateTimeRequired').val().toLowerCase() == "true");

answered Nov 15, 2011 at 19:31

amit_g

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