Intro to JavaScript Functions Default Parameters

Learning Objective: By the end of this lesson, students will be able to implement default parameters in JavaScript functions to handle missing arguments.

What if your function requires certain arguments, and you want to provide a default value for the parameter if an argument is not supplied when the function is invoked?

JavaScript has the option to specify default parameters. By specifying a default, name will always equal 'friend' unless an argument is supplied! This overrides the default behavior of name being undefined unless an argument is passed.

const sayHi = (name = 'friend') => {
  console.log(`Hi ${name}!`);
}

sayHi();
// Prints: 'Hi friend!'

sayHi('Joe');
// Prints: 'Hi Joe!'

Any expression can be provided as a default, including objects, functions, etc.