In JavaScript when verifying true condition
Below
if(variablename=='true')
is working but
if(variablename==true)
is not working. Any reasons for this? Is it specific to some browsers?
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j08691
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user3802115
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4What is `variablename` here? – Frxstrem Jun 20 '16 at 16:28
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1'true' !== true, 'true' is a string not a Boolean and shouldn't be used to check truthiness. – Tyler Biscoe Jun 20 '16 at 16:29
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1'true' and true are two different thing - one is string and another is boolean. – Muhammad Sumon Molla Selim Jun 20 '16 at 16:29
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Please read the documentation: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Equality. – Jun 20 '16 at 16:52
1 Answers
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Strings and booleans aren't the same thing at all. Non-empty strings are all equivalent to true (How can I convert a string to boolean in JavaScript?). You need to determine what the type of variablename is and implement the appropriate comparison.
The difference between 'true' and true is similar to the differences between '3' and 3, or 3.0 and 3. In many cases they will "work". Using these assumptions and implicit coercions is not safe and will eventually cause trouble.
Languages such as JavaScript that support implicit coercions give you plenty of rope. It's up to you to not hang yourself with it.
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Robert Columbia
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2How are `3.0` and `3` different? And no, the difference between `'3'` and `3` is **not** similar to the difference between `'true'` and `true`. Nor is it correct to say that "non-empty strings are all equivalent to true". I guess what you meant to say is that "non-empty strings are considered true in a boolean context (in other words, 'truthy')". – Jun 20 '16 at 16:46
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