Sometimes you want to convert one data type into another data type without changing the values manually.

For instance, you might want to convert a number to a string. JavaScript sometimes does this implicitly.

Like when you use the double equals operator (==), or when you attempt to do something on a value with a data type that is incompatible with the operation. This is called Type Coercion.

This said, you can also convert data types explicitly. And I'm going to show you how to do that in this article.

The string data type is a very common data type in JavaScript. For almost every other data type, you need to have a string representation.

Just as you must have seen something similar to "[object Object]" when you use an object in place of an actual string.

In this article, we'll learn what the toString method is, and how to convert a number (and a few other data types) to a string using this method.

The toString method

As the name implies, this method is used to change data to a string. Arrays, numbers, and booleans each have this method which converts their data in various ways. Let's look at them individually now.

How to convert a number to a string

The toString method exists on every number literal. It converts numbers to their string representations. Here's how it is used:

const num = 54;
// "54"

But there's more to this. The toString method for numbers also accepts a base argument. This argument allows you to convert a number to another base.

The returned value is the string representation of the new number. Here's how it is used:

const num = 54;
const num2 = num.toString(2);
// "110110"

parseInt is another JavaScript method which in contrast converts strings to their respective number representations. Here's how it works:

const numInStr = "54";
const str = "Hello";
// 54
// NaN

For a variable not similar to a number, parseInt returns Nan as seen above.

How to convert an array to a string in JavaScript

Arrays also have the toString method. The returned value of this method is a concatenation of all values of the array (and deep-nested arrays in it) separated by commas. Here's how it is used:

const arr = ["javascript", "toString", [1, "deep1", [3, 4, "array"]]];
// "javascript,toString,1,deep1,3,4,array"

How to convert an object to a string in JavaScript

The return value of toString on an object is - just as you may have often come across - "[object Object]". For example:

const obj = {name: 'Object'};
const obj2 = {type: 'data', number: 100};
// [object Object]
// [object Object]

The default conversion of objects to string is [object Object]. Notice that there are two objects there, and not just one? And the other is capitalized?

There are more representations for objects like what follows:

function print() {};
const arr = [];
const obj = {};
// [object Function] [object Array] [object Object]

Functions, Arrays, Objects, and even Dates and Regex are all objects. And each of them has the toString method.

When toString is called on them, it grabs whatever class of Object the value is, and then prints it it like you see above ("Function, Array, Object).

We use call(variable) because the toString gets the object class through the this property.


The .toString method returns a string conversion of the data it is used on. This is very useful for certain cases, especially numbers.

In this article, we learned how the JavaScript toString method works with numbers, arrays and objects and we also looked a little at parseInt.