Javascript returns false on run, but my logic and the console says it's true

I've a problem with a conditional in Js. The logic says that the answer should be false, and according to the console, the statement is false, but when I run it, Js says it's true! It is:

//assume that the value of x is a string different from ''

if(document.getElementById('x').value === ''){
    //do some things
}
else{
    //do other things
}

When I put on the console

document.getElementById('x').value === ''

it returns false, as spected. When I run, Js deals with it like it was true, jumping to the

//do some things

I tried to make it like

if('' === document.getElementById('x').value)

tried to

var s = document.getElementById('x').value;
if(s.isEmpty())

and also

var s = document.getElementById('x').value;
if(s.equals(''))

but none worked. The code is run way after the DOM has loaded, so it's not like it was trying to check an inexisting element.