Null
In JavaScript, null is a special value that represents an empty value.
let number = null;
The code above suggests that the number variable is empty at the moment.
null is falsy
Besides false, 0, an empty string (''), undefined, NaN, null is a falsy value. It means that JavaScript will coerce null to false in conditionals.
const message = null;
if (message) {
console.log('No Messages');
} else {
console.log('Message');
}
// Output : "Message"
In this example, the message variable is null therefore the if statement evaluates it to false and executes the statement in the else clause.
typeof null is object
console.log(typeof 25) // Output : 'number'
console.log(typeof null); // Output : ‘object’
undefined
If a variable is declared but the value is not assigned, then the value of that variable will be undefined
let name;
console.log(name); // Output : undefined
typeof undefined is undefined
let name;
console.log(typeof(name)); // Output : ‘undefined’
Null vs undefined
null is an assigned value. It means nothing.
undefined means a variable has been declared but not defined yet.
null is an object. undefined is of type undefined.
null !== undefined but null == undefined.
