JavaScript: Numbers

When you're working with numbers, it's important to understand addition versus concatenation. Addition gives you the sum of two numbers, whereas concatenation just joins or "sandwiches" the two values together.

For example, here's addition:

var x = 10;
var y = 5;
console.log (x + y)

The result would be 15.

However, if one of the values is a string rather than a regular number, the result will be concatenated instead of added. A string is identified by quotations; numbers do not have quotations.

var x = "10";
var y = 5;
console.log (x + y)

The result would be 105. The two values get joined together.

Not a Number (NaN)

If you try to multiply a string by a number, the result will be NaN, which means "Not a Number."

You would see NaN if you tried to run something like this:

var x = "Touchdown!";
var y = 5;
console.log (x * y);

The result would be NaN, because 5 times a touchdown doesn't yield a number.

The Math Object

JavaScript has a built-in Math object that you can use to do various things with numbers. For example,

var x = 5.8;
//round the value of x
var y = Math.round(x);

This will round the value of the x variable, resulting in 6.

Other methods you can apply to the Math object include .max, .min, .random.

About Tom Johnson

I'm a technical writer / API doc specialist based in the Seattle area. In this blog, I write about topics related to technical writing and communication — such as software documentation, API documentation, visual communication, information architecture, writing techniques, plain language, tech comm careers, and more. Check out my API documentation if you're looking for more info about that. If you're a technical writer and want to keep on top of the latest trends in the field, be sure to subscribe to email updates below. You can also learn more about me or contact me. Finally, note that the opinions I express on my blog are my own points of view, not that of my employer.