JavaScript How to Convert Array to String Easily

You can convert an array to a string in JavaScript by using array.join(separator) to join elements with a separator or array.toString() which joins elements with commas by default.

Examples

Input[1, 2, 3]

Output"1,2,3"

Input["apple", "banana", "cherry"]

Output"apple,banana,cherry"

Input["a", "b", "c"].join("-")

Output"a-b-c"

How to Think About It

To convert an array to a string, think about how you want the elements to appear joined together. You can use join() to specify a separator like a comma, space, or dash, or use toString() which automatically joins elements with commas.

Algorithm

1

Get the input array.

2

Choose a method to convert it to string: either <code>join()</code> or <code>toString()</code>.

3

If using <code>join()</code>, decide on a separator string.

4

Call the chosen method on the array.

5

Return the resulting string.

Code

javascript

const fruits = ["apple", "banana", "cherry"];
const result1 = fruits.toString();
const result2 = fruits.join(" - ");
console.log(result1);
console.log(result2);

Output

apple,banana,cherry
apple - banana - cherry

Dry Run

Let's trace converting ["apple", "banana", "cherry"] to string using join(" - ")

1

Start with array

["apple", "banana", "cherry"]

2

Call join with separator " - "

"apple" + " - " + "banana" + " - " + "cherry"

3

Return joined string

"apple - banana - cherry"

Index	Element	String after join step
0	apple	apple
1	banana	apple - banana
2	cherry	apple - banana - cherry

Why This Works

Step 1: Using toString()

toString() converts the array elements into a comma-separated string automatically.

Step 2: Using join(separator)

join() lets you specify how to connect elements, like spaces, dashes, or no separator.

Alternative Approaches

Using JSON.stringify()

javascript

const arr = [1, 2, 3];
const str = JSON.stringify(arr);
console.log(str);

This converts the array to a JSON string including brackets and quotes, useful for data transfer but not for simple joining.

Using a loop to build string

javascript

const arr = ['a', 'b', 'c'];
let str = '';
for (const item of arr) {
  str += item;
}
console.log(str);

Manually concatenates elements without separators; less efficient and more code.

Complexity: O(n) time, O(n) space

Time Complexity

Converting an array to string requires visiting each element once, so it takes O(n) time where n is the number of elements.

Space Complexity

The output string stores all elements joined, so it uses O(n) space proportional to the input size.

Which Approach is Fastest?

toString() and join() have similar performance; join() is preferred for flexibility.

Approach	Time	Space	Best For
toString()	O(n)	O(n)	Quick comma-separated string
join(separator)	O(n)	O(n)	Custom separator strings
JSON.stringify()	O(n)	O(n)	Full JSON format with brackets
Manual loop concat	O(n)	O(n)	Custom complex formatting but verbose