JavaScript Introducing ES2015 The Cooler Parts of ES2015 Default Parameters

Natalie Cluer
Natalie Cluer
18,884 Points

undefined vs null?

Why do we pass in undefined as a parameter? what would the difference be between passing in undefined vs passing in null?

2 Answers

Stuart Wright
Stuart Wright
41,064 Points

By using undefined, you are telling the function that you are choosing not to pass an argument in for name, so it knows to use the default value. By passing in null, you are telling it that you are passing in the value null as your name argument.

greet(undefined, 'Afternoon');

> Good Afternoon, Guil! 
greet(null, 'Afternoon');

> Good Afternoon, null!