JavaScript Fundamentals on Coderrob

JavaScript Arrow Functions Explained

Mon, 27 Apr 2026 11:30:00 -0500

Arrow functions are compact JavaScript functions with a few deliberate differences from ordinary functions.

They are excellent for small transformations and callbacks. They are not a universal replacement for function, and treating them like one hides the exact behavior that makes them useful.

Use an arrow when you want a concise function and do not need the function to define its own this, arguments, or constructor behavior.

The Basic Syntax

An ordinary function expression looks like this:

JavaScript 'this' Explained

Mon, 27 Apr 2026 11:00:00 -0500

JavaScript’s this is not difficult because it does many things. It is difficult because one small word changes value based on how a function is called.

That makes this look unpredictable when the real problem is usually that we are looking in the wrong place.

For an ordinary function, do not start with where the function was written. Start with the call-site.

The call usually decides this.

That one rule explains most of the behavior you will meet in day-to-day JavaScript.

JavaScript Closures and Modified Closures Explained

Mon, 27 Apr 2026 10:00:00 -0500

Closures show up any time a JavaScript function uses a variable defined from outside its own curly braces.

That makes them common in callbacks, event handlers, timers, factory functions, and plenty of code that passes functions around.

This post is about two questions:

What is a closure?
What happens when a closed-over variable is modified before the function uses it?

The short version:

A closure happens when a function keeps access to variables from its surrounding scope, even after that outer scope has finished running.

JavaScript Hoisting Explained

Sun, 26 Apr 2026 10:00:00 -0500

Hoisting is JavaScript’s setup behavior for declarations.

It affects whether a function or variable can be used before the line where it appears in the file. That matters because function, var, let, and const do not all behave the same way.

This post is about two questions:

When does JavaScript create the name?
What value, if any, is available before the declaration line runs?

Hoisting is usually explained as “JavaScript moves declarations to the top.”

JavaScript Var, Let, and Const Explained

Sat, 25 Apr 2026 10:00:00 -0500

Most JavaScript code starts with a simple act: you give a value a name. We call that a variable declaration.

That sounds small, but the way you create that name affects how the rest of your code can use it. A variable might be available only inside a small “if” block, across an entire function, or in places you did not really mean to share it.

That is why var, let, and const are worth understanding before the code gets complicated.

JavaScript Promise

Wed, 22 Oct 2025 21:00:00 -0500

A Promise is a guaranteed placeholder value for what a function or series of functions will return.

It’s a promise to return a value eventually.

The function swears this time is different. You can trust it. It swears it’ll get it back to you in no time.

If you haven’t already, check out my post on JavaScript Callbacks where we dove into callback hell and why we desperately needed something better. Spoiler: Promises are that something better.

JavaScript Spread Syntax Explained

Thu, 03 Mar 2022 21:28:27 -0600

JavaScript’s spread syntax, ..., lets you expand one value into another context. It is small, useful, and easy to misunderstand.

The practical version is this:

In an array literal, spread adds values from an iterable.
In a function call, spread passes values from an iterable as separate arguments.
In an object literal, spread copies an object’s own enumerable properties.

Spread expands a source into the place where you use it.

JavaScript Callbacks

Mon, 03 May 2021 15:00:00 -0500

Brief History of Callbacks

It all starts with the callback function.

A callback function is just a plain JavaScript function that is passed into another function as an argument.

That’s it. Nothing special.

This callback function can be used to return data, or to signal that some event took place.

If you’ve worked with web development you’ve definitely crossed paths with callbacks.

Think of a button click event for a web page.

JavaScript Function Parameters and Arguments Explained

Thu, 17 Sep 2020 00:46:15 -0500

JavaScript Function Signatures

Alright, you’ve probably seen functions before. Something like this maybe?

 function doSomething(name, desc, task) {
 // did something
 }

This function, named doSomething, takes three parameters as part of its function signature. These parameters named name, desc, and task are the names of the values being sent into the function.

I’m going to use a sportsball reference here so be warned. You can think of the function as a net that gets various types of objects tossed into the hoop ( ) where it triggers sports points.