JavaScript 101: the basics (cont’d)

tenor (13)

“I could never learn to code– I hated math in high school.”

That’s one of the most common things I hear from people when I mention how surprised I was (am?) that I ended up being a professional computer nerd for a living.

Even for the people I talk to who are open to the idea of learning how to code (if only for the variety of doors and opportunities it will open for them if not for the fun of coding itself), they still find the idea of doing math professionally a somewhat extremely daunting and unpleasant prospect.

The good news: you don’t have to be Einstein, Oppenheimer, Feynman, or any other world-renowned mathematician or physicist to be a software engineer.

The bad news:  you will probably have to brush up on some basics up through algebra (and possibly geometry, if you end up getting into front-end data analytics visualizations). So if this was you after your last math class ever…

tenor (14)

…I just want you to know that I’m laughing at you a little bit 😝

Mathematical Operators

In my last post, we covered basic data types and printing to the console, which will be your new best friend for a little while. For obvious reasons, mathematical operators in code are primarily used to manipulate data in the form of numbers, but as we’ll see shortly, they can also be used to mutate strings.

In the following examples, we’ll be using the mathematical operators inside the console.log function, which will print the result to the console (denoted by the comments). It should be pretty straightforward:

console.log( 2 + 4 ); // 6
console.log( 4 - 2); // 2
console.log( 2 * 4); // 8
console.log( 4 / 2); // 2

Side note: you can use the + operator on strings, like so:

console.log('I have the ' + 'best cat.'); // 'I have the best cat.'

There are a few other useful built-in JavaScript tools that will also help you crunch your coding numbers. In JavaScript, there is a built-in series of functions that will do a lot of the hard work for you called Math methods.

These are really useful for rounding non-integer numbers up, down, or whichever is closest:

Math.floor(3.5234); // 3
Math.ceil(4.5902); // 5
Math.floor(-1.3902); // -2
Math.ceil(-3.4992); // -3
Math.round(3.4); // 3

There is also a method for randomly producing a value between 0 and 1.

Math.random(); // returns something between 0 and 1

The Modulo

One important operator that you may not be familiar with from grade school math class is called the modulo. Its symbol is the % sign. What it does is return the remainder of one number divided by another. Examples:

console.log( 5 % 4 ); // 1
console.log( 28 % 2 ); // 4
console.log( 10 % 5 ); // 0

Note that dividing 10 by 5 has no remainder at all, since 5 goes into 10 exactly twice.

tenor (16)
See that wasn’t so bad, was it?

Questions, comments, and constructive/corrective feedback always appreciated.

4 thoughts on “JavaScript 101: the basics (cont’d)

    1. Hey there! Don’t beat yourself up about it– decimal math is weird in JavaScript. Here’s a post that explains some of the nuance of adding decimals in JS pretty well:

      I wrote a few console logs to demonstrate the difference between 0.1 + 0.2 and 0.3 for you here:

      Also, as a good best practice, I would use the === instead of == to test for equality between two things in JS. The double-equals will work most of the time, but as you start developing more complex and specific algorithms to solve problems with code, you’ll find that triple-equals (a.k.a. “strict equals”) will be a more accurate test to use in your control flow. Good luck!


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