JAVASCRIPT

javascript default function parameter value

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

javascript Passing Parameter as Default Values

function sum(x = 1, y = x,  z = x + y) {
    console.log( x + y + z );
}

sum(); // 4

javascript Passing Function Value as Default Value

// using a function in default value expression

const sum = () => 15;

const calculate = function( x, y = x * sum() ) {
    return x + y;
}

const result = calculate(10);
console.log(result);            // 160