Why javascript treats 0 equal to empty string?

0, "" (Empty String), false all technically have the same value, when typecasted. If you need to strictly treat them, you can use ===.

It is the same with similar programming languages, like PHP.

var a = 0;
var b = ''; //empty string
if(a == b){
    console.log('equal'); //this is printed in console
}else{
    console.log('not equal');
}

To make a strict comparison:

if(a === b){
    console.log('equal');
}else{
    console.log('not equal'); //this is printed in console
}

== operator in javascript don't compare types so 0=='' === true (because as a number string '' evaluates to 0) or 0==false === true (because bool false evaluates to 0) to compare types to you can use === operator.

Here you'll find useful information about comparison.

Because empty string represented as number is zero. If you compare apples and oranges you should think of how your particular orange would look if it were an apple.