What exactly is Type Coercion in Javascript?

Question

What exactly is type coercion in Javascript?

For example, on the use of == instead of ===?

Answer 1

var str = 'dude';
console.log(typeof str); // "string"
console.log(!str); // false
console.log(typeof !str); // "boolean"

Example of a variable which is initially declared as a string being coerced into boolean value with the ! operator