JAVASCRIPT

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);

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"

unlimited optional arguments js

// arguments is "like" an array that stores all arguments given to manyArgs
// (User can invoke manyArgs with arguments even though none are specified)
function manyArgs() {
  for (var i = 0; i < arguments.length; ++i)
    alert(arguments[i]);
}
// Note: for arrow functions you must do
let manyArgs = (concreteArg1, concreteArg2, ...rest) => {
  for (var i = 0; i < rest.length; ++i)
    alert(rest[i]);
  	// concreteArgs are not included in rest "array"
}

javascript How can i do optional function

const db = { input() { return { query() { return 'db.input(...).query(...)'; } } }, query() { return 'db.query(...)'; } };

console.log((true ? db.input() : db).query());
console.log((false ? db.input() : db).query());