Convert Array to comma separated String in JavaScript

Convert Array to comma-separated String #

To convert an array to a comma-separated string, pass the array as a parameter to the String object - String(arr). The String object will convert the passed in array to a comma-separated string and return the result.

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const arr = ['one', 'two', 'three'];

const str = String(arr);
console.log(str); // 👉️ 'one,two,three'
console.log(typeof str); // 👉️ string

The only parameter we passed to the String object is the value we want to convert to a string.

Since we provided an array, the result is a comma-separated string.

An alternative, but also very common approach is to use the Array.join method.

To convert an array to a comma-separated string, call the join() method on the array, passing it a string containing a comma as a parameter. The join method returns a string containing all array elements joined by the provided separator.

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const arr = ['one', 'two', 'three'];

const str = arr.join(',');
console.log(str); // 👉️ 'one,two,three'
console.log(typeof str); // 👉️ string

The only parameter the Array.join method takes is a separator. For our use case, we provide a comma as the separator.

The method returns a string containing all array elements joined by the provided separator.

You can pass any value as the separator to the Array.join method, here are other examples.

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const arr = ['one', 'two', 'three'];

const withSpaces = arr.join(' ');
console.log(withSpaces); // 👉️ 'one two three'

const withCommaAndSpace = arr.join(', ');
console.log(withCommaAndSpace); // 👉️ one, two, three

const withDashes = arr.join('-');
console.log(withDashes); // 👉️ 'one-two-three'

const withoutSeparator = arr.join('');
console.log(withoutSeparator); // 👉️ onetwothree

If you call the join method on an empty array, it returns an empty string.

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console.log([].join(',')); // 👉️ ''

An important thing to note is that if the array contains elements that are undefined, null or empty array [], they get converted to an empty string.

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const arr = ['one', 'two', null];

console.log(String(arr)); // 👉️ one,two,
console.log(arr.join(',')); // 👉️ one,two,

Further Reading #

• Convert Array to String without Commas in JavaScript
• Convert an Array to a String in JavaScript