How to convert array to object in JavaScript

Converting arrays to objects is a common task in JavaScript. There are several approaches depending on your data structure and requirements.

Method 1: Array of Arrays to Objects with Alphabetic Keys

Let's convert a nested array structure into objects with keys as English alphabet letters:

const data = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]];
const dataArr = data.map(arr => {
    return arr.reduce((acc, cur, index) => ({
        ...acc,
        [String.fromCharCode(97 + index)]: cur
    }), Object.create({}))
});
console.log(dataArr);

[
    { a: 1, b: 2, c: 3, d: 4 },
    { a: 5, b: 6, c: 7, d: 8 },
    { a: 9, b: 10, c: 11, d: 12 }
]

Method 2: Simple Array to Object with Index Keys

Convert a simple array to an object using array indices as keys:

const fruits = ['apple', 'banana', 'orange'];
const fruitsObj = Object.assign({}, fruits);
console.log(fruitsObj);

// Alternative using spread operator
const fruitsObj2 = {...fruits};
console.log(fruitsObj2);

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

Method 3: Array to Object with Custom Keys

Create objects from arrays using custom key-value mapping:

const names = ['John', 'Jane', 'Bob'];
const ages = [25, 30, 35];

const people = names.reduce((acc, name, index) => {
    acc[name] = ages[index];
    return acc;
}, {});

console.log(people);

{ John: 25, Jane: 30, Bob: 35 }

Method 4: Using Object.fromEntries()

Convert an array of key-value pairs into an object:

const entries = [['name', 'John'], ['age', 30], ['city', 'New York']];
const person = Object.fromEntries(entries);
console.log(person);

// From array with map
const colors = ['red', 'green', 'blue'];
const colorObj = Object.fromEntries(
    colors.map((color, index) => [color, index])
);
console.log(colorObj);

{ name: 'John', age: 30, city: 'New York' }
{ red: 0, green: 1, blue: 2 }

Comparison

Conclusion

Choose the method based on your data structure: use reduce() for complex transformations, Object.assign() for simple conversions, and Object.fromEntries() for key-value pair arrays. Each method serves different conversion needs efficiently.