Check for false

Question

Is there any better way of doing this?

if(borrar() !== false)
{
    alert(\'tatatata bum bum bum prapra\');
}
return false;

Answer 1

If you want it to check explicit for it to not be false (boolean value) you have to use

if(borrar() !== false)

But in JavaScript we usually use falsy and truthy and you could use

if(!borrar())

but then values 0, '', null, undefined, null and NaN would not generate the alert.

The following values are always falsy:

false,
,0 (zero)
,'' or "" (empty string)
,null
,undefined
,NaN

Everything else is truthy. That includes:

'0' (a string containing a single zero)
,'false' (a string containing the text “false”)
,[] (an empty array)
,{} (an empty object)
,function(){} (an “empty” function)

Source: https://www.sitepoint.com/javascript-truthy-falsy/

As an extra perk to convert any value to true or false (boolean type), use double exclamation mark:

!![] === true
!!'false' === true
!!false === false
!!undefined === false

Answer 2

Checking if something isn't false... So it's true, just if you're doing something that is quantum physics.

if(!(borrar() === false))

or

if(borrar() === true)

Answer 3

If you want to check for false and alert if not, then no there isn't.

If you use if(val), then anything that evaluates to 'truthy', like a non-empty string, will also pass. So it depends on how stringent your criterion is. Using === and !== is generally considered good practice, to avoid accidentally matching truthy or falsy conditions via JavaScript's implicit boolean tests.

Answer 4

You can use something simpler:

if(!var){
    console.log('var is false'); 
}

Answer 5

Like this:

if(borrar())
{
   // Do something
}

If borrar() returns true then do something (if it is not false).

Answer 6

If you want an explicit check against false (and not undefined, null and others which I assume as you are using !== instead of !=) then yes, you have to use that.

Also, this is the same in a slightly smaller footprint:

if(borrar() !== !1)