js optional parameter code example

Example 1: javascript constructor default parameter

function greet(name, greeting, message = greeting + ' ' + name) {
  return [name, greeting, message]
}

greet('David', 'Hi')                     // ["David", "Hi", "Hi David"]
greet('David', 'Hi', 'Happy Birthday!')  // ["David", "Hi", "Happy Birthday!"]

Example 2: javascript optional parameters

const myFunction = (str, id=0) => {
	console.log(str, id)
} 
myFunction("Hello Grepper")
// OUTPUT : "Hello Grepper 0"

myFunction("HG", 10)
// OUTPUT : "HG 10"

Example 3: optional function parameter javascript

function check(a, b = 0) {
  document.write("Value of a is: " + a + 
                 " Value of b is: " + b + 
                 "<br>");
}
check(9, 10);
check(1);

Example 4: variable defaults javascript es6

let variableToSet = checkedValue || defaultValue;