Converting an Array to JSON Object in JavaScript

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JSON, or “JavaScript Object Notation”, is one of the most popular data exchange formats, particularly in web development. If you have an array of data but the program you’re communicating with requires an object, don’t fear, we’ll go over some easy conversion methods.

Quick Answer – JS Array to JSON

Arrays are actually valid JSON, so if you just need to prepare your array in order to make a fetch request with it, it’s as easy as using the JSON.stringify() method.

const resp = await fetch('https://example.com', {
    method: 'POST',
    mode: 'cors',
    headers: {
      'Content-Type': 'application/json'
    },
    body: JSON.stringify([1, 2, 3, 4, 5])
  });

The JSON.stringify() method converts a JavaScript object, array or value to a JSON string that can be sent over the wire using the Fetch API (or another communication library).

Weird Answer – Array to JSON with indexes as keys

If you didn’t want the direct string representation of a JSON array, perhaps you want an object where the keys are the indexes of the array. For example:

["apple", "orange", "banana"]

// becomes

{
  "0": "apple",
  "1": "orange",
  "2": "banana"
}

To get a JSON object from an array with index keys you can use the Object.assign method in conjunction with JSON.stringify following code:

const array = ["apple", "orange", "banana"]
const jsonString = JSON.stringify(Object.assign({}, array))
// jsonString becomes
// {"0":"apple","1":"orange","2":"banana"} 

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