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Converting Javascript array to string

/ by Ava Taylor

JavaScript arrays are super handy. You can store all kinds of data in them—from numbers to strings to objects. But what if you want to turn that array into a single long text string?

Maybe you want to show it on your website. Or save it in local storage. Or email it to your dog. (Okay, maybe not that last one…)

Whatever the reason, let’s learn how to convert arrays to strings in JavaScript.

TL;DR (Too Long; Didn’t Read)

There are several easy ways to turn a JavaScript array into a string. The most common method is join(), which lets you choose a custom separator. You can also use toString(), but it gives you less control. Your choice depends on how you want the final string to look.

Why Convert Arrays to Strings?

Arrays are awesome for storing lots of similar items. But strings are better when you need to:

  • Display your data on a web page
  • Save your data in a file
  • Send your data over the internet

Strings are also easier to copy, store, and log. So knowing how to switch between arrays and strings is a useful trick!

The join() Method – Your New Best Friend

This is the superhero of array-to-string conversion. The join() method turns all the items in your array into a string. And you get to choose what goes in between each item!

Here’s the basic use:

let fruits = ["apple", "banana", "cherry"];
let fruitString = fruits.join(", ");
console.log(fruitString); // "apple, banana, cherry"

Nice and easy, right?

You can use join() with different separators too:

let words = ["Hello", "world"];
let sentence = words.join(" ");
console.log(sentence); // "Hello world"

Want a dash-separated string?

let colors = ["red", "blue", "green"];
let colorString = colors.join("-");
console.log(colorString); // "red-blue-green"

That’s how flexible join() is—you get total control over what string comes between your elements.

What About toString()?

Okay, so toString() also converts an array into a string. But it doesn’t let you customize the separator. It just puts commas between your array items.

Here’s an example:

let numbers = [1, 2, 3, 4];
let numberString = numbers.toString();
console.log(numberString); // "1,2,3,4"

So, if you’re okay with those default commas, toString() works fine. But join() is better if you want more control.

What Happens with Mixed Data?

JavaScript arrays can hold all kinds of stuff. Numbers, strings, booleans, even other arrays! When you convert mixed arrays to strings, JavaScript turns all the elements into their string version before combining them.

let mixed = ["Age:", 30, true];
let mixedString = mixed.join(" ");
console.log(mixedString); // "Age: 30 true"

Easy-peasy. Just remember: if any item inside the array is an array itself (a nested array), things get a little… weird:

let tricky = [1, [2, 3], 4];
console.log(tricky.join(", ")); // "1, 2,3, 4"

It flattens the inner array into a string! So watch out for nested arrays if you’re using join().

Use Cases – When Does This Come in Handy?

Here are just a few real-life situations where converting arrays to strings is useful:

  • Making tags for blog posts: “JavaScript, Arrays, String”
  • Creating CSV rows: “John,Doe,35”
  • Generating sentences: “I love pizza and soda.”

Even form fields like checkboxes often return arrays. You might want to turn them into a string to send to a server.

What About JSON.stringify()?

This one’s a little different. While it does turn arrays into strings, its main job is to prepare data for storage or sending via APIs.

Example:

let myArray = [1, 2, 3];
let jsonString = JSON.stringify(myArray);
console.log(jsonString); // "[1,2,3]"

Notice the quotes? Yep, your data is now in a string format that looks like JSON. This is perfect when you’re:

  • Storing data in localStorage
  • Sending data to a backend server
  • Saving user preferences

But it’s not great if you want line-by-line text or pretty spacing. That’s what join() is for.

Traps to Avoid

Let’s go over a few common gotchas:

  • Don’t blindly use toString(): You might get unexpected commas.
  • Don’t forget about nested arrays: Elements like [2, 3] can turn into “2,3”.
  • Empty arrays are still strings: [].join(“anything”) gives you “”.

Always know what you’re working with!

Mini Challenge – Practice Time!

Try converting the following arrays into strings using different methods:

  1. [“Tom”, “Jerry”, “Spike”] → “Tom vs Jerry vs Spike”
  2. [42, true, “hello”] → “42|true|hello”
  3. [1, [2, 3], 4] → ? (watch out!)

Use join() and experiment with different separators to see what you get!

Bonus: Join With an Empty String!

Eyeing those social handles or hashtags? Need to smush it all together?

let hashtags = ["#NoFilter", "#SunnyDay", "#Vacation"];
let combined = hashtags.join("");
console.log(combined); // "#NoFilter#SunnyDay#Vacation"

join(“”) removes all separators. Perfect for squishing things together!

Wrap-Up: Which Method Should You Use?

Let’s see a quick recap:

Method Use Case Separator Option?
join() Custom string output Yes
toString() Quick conversion No
JSON.stringify() Data storage/API use No

Conclusion

Turning an array into a string in JavaScript is easy and often super useful. Whether you’re showing data in a UI, sending it somewhere, or saving it, these methods make your job easier.

Just remember: use join() when you can customize, toString() for simplicity, and JSON.stringify() for structured data.

Now go forth and string those arrays like a JavaScript ninja!

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