What does an exclamation mark before a variable mean in JavaScript

Question

I\'m trying to learn JavaScript by going through some code in an application and I keep seeing !variable in if conditions. For example:

if (!va         


        

Answer 1

It is a negation operator used for truth tests on a variable.

var myVariable = 1;

if ( ! myVariable )
{
    // myVariable evaluates as false
}

if ( myVariable )
{
    // myVariable evaluates as true
}