Lecture: Functions in JS

with Carmen Salas • 2024/09/30

slides

• Basic Concepts

• Functions in JavaScript

• Console.log vs Return

• Parameters vs Arguments

• Testing our Code

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Basic Concepts

variables are containers for values (strings, numbers, booleans, etc.) In ES6 (EcmaScript6), we use either let or const.

• let allows variable re-definition

• const doesn't! Although some types/objects like Arrays can work around this to an extent.

• var keyword is no longer used in modern JS practices but it used to serve both the purposes of let and const with the key difference being that it is NOT block-scoped.

Functions in JavaScript

A JavaScript function is a block of code designed to perform a particular task, and is executed when it is invoked or called.

Typical function syntax:

   function hello (name) {
      return "hello" + name;
   };

• function - JS keyword for defining functions

• hello - function name

• name - function parameter

• return "hello" + name; - function body (anything in between the curly braces is considered as such)

Arrow function syntax:

   const hello = (name) => {
      return "hello" + name;
   };

• no keyword function - hello - is the variable name, and also serves as the function name

• without a name (in this case, hello) and the const keyword, the function becomes anonymous

Console.log vs Return

• console.log is essentially a print function

• return is used, within a function body, to terminate it and optionally return a value

Parameters vs Arguments

   const hello = (name) => {
      return "hello" + name;
   };

   hello("Motun");

• name - function parameter (placeholder for arguments)

• "Motun" - function argument (value passed into a function when it is invoked)

Testing our Code

Just console.log() it.