How to Initialize an Array of Objects in JavaScript

Initialize an Array of Objects in JavaScript #

Use the fill() method to initialize an array of objects, e.g. new Array(2).fill({key: 'value'}). The Array() constructor creates an array of a specified length and the fill() method sets the elements in an array to the provided value and returns the result.

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const arr1 = new Array(2).fill({key: 'value'});

// 👇️ [{key: 'value'}, {key: 'value'}]
console.log(arr1);

The parameter we passed to the Array() constructor is the number of empty elements the array should contain.

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console.log(new Array(2)); // 👉️ [ , ]

What the Array() constructor does under the hood is, it sets the array's length to the provided value.

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const arr = [];
arr.length = 2;

console.log(arr); // 👉️ [ , ]

We need an array of N empty elements, so we can replace the value of each element with an object using the fill() method.

Each of the 2 elements in the array gets assigned a value of an object.

Alternatively, you can use a simple for loop.

Initialize an Array of Objects using for loop #

To initialize an array of objects, use the Array() constructor to create an array filled with N empty elements and use a for loop to iterate over the array assigning each element to an object.

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const arr2 = new Array(2);

for (let i = 0; i < arr2.length; i++) {
  arr2[i] = {key: 'value'};
}

// 👇️ [{key: 'value'}, {key: 'value'}]
console.log(arr2);

We used the Array() constructor to create an array of 2 empty elements.

The for loop allows us to iterate over the array and assign each empty element to an object.

Further Reading #

• Initialize an Array of Boolean Values in JavaScript
• Create a Zero filled Array in JavaScript