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True Is Not Always True In JavaScript
Hello everyone
In this article, I will try to explain the behaviour of the boolean
data type of JavaScript.
We often use if
statements in JavaScript to check if a value, that can be of any data type is true
or false
. But do you know that these values are not really true
or false
, rather they are considered as truthy
or falsy
values?
Explanation
Let's understand this with an example.
var val = "blog";if (val) { console.log(true);}
So in the above code snippet, we declared a variable val
which is storing a string "blog"
.
In general, if
statements expect a boolean expression or a boolean condition but here we are passing the variable val
directly without any boolean expression.
And this if
statement evaluates the value of val
to true
and execute its block. But why?
Why
In JavaScript, any non-zero number including the negative numbers and non-empty strings are termed as truthy
values and the truthy
values are translated to boolean true
when evaluated in a Boolean context.
So in our example, as the value of the variable val
is a string with data i.e, not empty, it is considered as a truthy
value which evaluates to true
in the if
statement condition.
And the values other than the truthy
values are termed as falsy
values.
falsy
values in JavaScript.
false
null
undefined
0
NAN
''
""
0n
-0
Conversion
Convert the truthy
and falsy
values to boolean true
or false
.
You can pass the truthy
or falsy
value to the Boolean()
and it will return true
or false
.
var val = "blog";if (Boolean(val)) { console.log(true);}
Or you can use the following syntax to convert it to a pure boolean value.
var val = "blog";if (!!val) { console.log(true);}
We know this truthy
or falsy
concept is not so impacting but it is always better to handle pure boolean values.
Originally published on blog.bibekkakati.me
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Original Link: https://dev.to/bibekkakati/true-is-not-always-true-in-javascript-2n7m
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