Skip to content

Latest commit

 

History

History
106 lines (71 loc) · 2.62 KB

notes.md

File metadata and controls

106 lines (71 loc) · 2.62 KB

Functions

Essential Questions

Why are functions a key feature of any programming language?

  • Less repetition
  • Break up our program into smaller pieces
  • Define reusable functionality (abstraction through parameters and arguments)
function rollDice(numSides) {
  let diceRoll = Math.ceil(Math.random() * numSides)
  console.log(diceRoll)
}


rollDice(6); // roll 6 sided
rollDice(20); // roll 20 sided

What is the difference between a function argument and a function parameter?

  • parameter is a placeholder (shadow/understudy)
  • argument is the actual value to take a parameter's place (star)

How do we declare functions in JavaScript?

  • function declaration (using function keyword)
function name(param1, param2) {
    return "something"
}
  • function expression (storing an anonymous function in a variable)
const name = function(param) {
    return "something";
}
  • arrow function (also storing a function in a variable using () => {} syntax)
const name = (param) => "something";

How does a function declared using function declaration notation differ from a function declared as function expression?

  • function declarations are hoisted
  • function expressions / arrow functions are NOT

What are arrow functions? In what ways are they similar to function expressions? In what ways are they different?

  • arrow functions are used mostly when passing functions as arguments:
  • arrow functions and function expressions are both stored in variables
const mahaba = ['ben', 'carmen', 'motun]

What does hoisting mean and how does it impact the way that we write our JavaScript programs?

Hoisting is a behavior of JavaScript where Function Declarations are pulled to the top of their respective scope. This means that we can call functions before we declare them.

This code will work:

sayHello("Ben"); // prints "Hello Ben"

function sayHello(name) {
    console.log(`Hello ${name}`);   
}

How does JavaScript handle extra arguments during function invocation? What about missing arguments?

  • JavaScript ignores extra arguments
  • JavaScript treats missing arguments as undefined

Tips & Best Practices

  • Declare all new variables at the top of their scope (if you can)
  • Use function declaration syntax to create helper functions at the bottom of your file.
  • Use arrow functions instead of function expressions for cleaner syntax

Other Notes

Declaration vs. Initialization

// Declaration
let age;

console.log(age); // undefined

// Initialization (assignment)
age = 27; 

console.log(age); // 27


// Declaration + Initialization
const name = 'ben';