JAVASCRIPT

javascript default parameters

function multiply(a, b = 1) {
  return a * b;
}

js default parameter

function read_file(file, default_param = false) {
  // Code
}

js default parameter

function greeting (name = 'stranger') {
  console.log(`Hello, ${name}!`)
}

greeting('Nick') // Output: Hello, Nick!
greeting() // Output: Hello, stranger!

javascript default function parameter value

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

How Do Default Parameters Work in JavaScript?

// Default parameters let you assign a default value to a parameter when you define a function. For example:

function greeting(name, message = ”Hello”){
	console. log(`${messgae}  ${name}`)
}

greeting(‘John’); //output: Hello John

//you can also assign a new value to the default parameter 
//when you call the function

greeting(‘Doe’, ‘Hi’); //output: Hi Doe

JavaScript Default Parameters

function sum(x = 3, y = 5) {

    // return sum
    return x + y;
}

console.log(sum(5, 15));  // 20 
console.log(sum(7));        // 12
console.log(sum());          // 8

ES6: Set Default Parameters for Your Functions

const increment = (number, value = 1) => number + value;

Default function arguments in ES6

function sort(arr = [], direction = 'ascending') {
  console.log('I'm going to sort the array', arr, direction)
}

sort([1, 2, 3])
sort([1, 2, 3], 'descending')

Default Parameter Values in javascript

// Default Parameter Values in javascript
// Longhand:
function volume(l, w, h) {
    if (w === undefined)
      w = 3;
    if (h === undefined)
      h = 4;
    return l * w * h;
  }
console.log(volume(2)); //output: 24
  
// Shorthand:
volume_ = (l, w = 3, h = 4 ) => (l * w * h);
console.log(volume_(2)) //output: 24

ES6: Set Default Parameters for Your Functions

const resultDisplayArray = []; 
for(let i = 0; i < result.failure.length; i++) {
resultDisplayArray.push(`<li class="text-warning">${result.failure[i]}</li>`); 
}

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