set default value in js function code example

Example 1: default in javascript

const greet = (message = 'Hello World!') => console.log(message);

greet(); // prints 'Hello World!'
greet('Hello! Does this answer your question?') // prints 'Hello! Does this answer your question?'

Example 2: javascript default function parameter value

function multiply(a, b) {
  b = (typeof b !== 'undefined') ?  b : 1
  return a * b
}