Zero is ‘falsy’ in JavaScript

Numeric zero in JavaScript is a ‘falsy’ value.
If it is used in a conditional operator it will act as false.

Example:

var checkValue = function(value){
    var check = "";

    if(value){
       check = "it was "+value;
    }
    else{
       check = "no value";
    }

    return check;
}

// number; returns "no value"
console.log(checkValue(0)); 

// string; returns "it was 0"
console.log(checkValue("0"));

Related reading:

Falsy values – extract from “JavaScript: The Good Parts”
Truthy and falsy in JavaScript

Filed under: Front-end, JavaScript, false, falsy, JavaScript, js, Number, truthy

typeof NaN in JavaScript

The typeof NaN in JavaScript is number.
This is because NaN is a property of the Number object.

Example:

var num = Number("string value");
console.log(num); // returns NaN
console.log(typeof num); //returns 'number'

Background:

NaN stands for Not-a-number.
It is used to indicate that a value is not numeric.

Filed under: Front-end, JavaScript, JavaScript, js, NaN, Number, typeof