Transforming array to object JavaScript

Suppose we have an array of strings like this ?

const arr = [ 'type=A', 'day=45' ];

We are required to write a JavaScript function that takes in one such array. The function should construct an object based on this array. The object should contain a key/value pair for each string in the array.

For any string, the part before '=' becomes the key and the part after it becomes the value.

Method 1: Using for Loop

const arr = [ 'type=A', 'day=45' ];

const arrayToObject = (arr = []) => {
    const obj = {};
    for (let i = 0; i 

{ type: 'A', day: '45' }


Method 2: Using reduce()

A more functional approach using the reduce() method:

const arr = [ 'type=A', 'day=45', 'status=active' ];

const arrayToObjectReduce = (arr = []) => {
    return arr.reduce((obj, item) => {
        const [key, value] = item.split('=');
        obj[key] = value;
        return obj;
    }, {});
};

console.log(arrayToObjectReduce(arr));


{ type: 'A', day: '45', status: 'active' }


Method 3: Using Object.fromEntries()

The most concise approach using Object.fromEntries() and map():

const arr = [ 'name=John', 'age=30', 'city=Paris' ];

const arrayToObjectEntries = (arr = []) => {
    return Object.fromEntries(arr.map(item => item.split('=')));
};

console.log(arrayToObjectEntries(arr));


{ name: 'John', age: '30', city: 'Paris' }


Handling Edge Cases

Here's a robust version that handles missing values and multiple equals signs:

const arr = [ 'type=A', 'url=https://example.com', 'empty=', 'noequals' ];

const arrayToObjectSafe = (arr = []) => {
    const obj = {};
    arr.forEach(item => {
        const splitIndex = item.indexOf('=');
        if (splitIndex !== -1) {
            const key = item.substring(0, splitIndex);
            const value = item.substring(splitIndex + 1);
            obj[key] = value;
        }
    });
    return obj;
};

console.log(arrayToObjectSafe(arr));


{ type: 'A', url: 'https://example.com', empty: '' }


Comparison

Conclusion

Use Object.fromEntries() with map() for the cleanest code in modern environments. For maximum compatibility, stick with the traditional for loop approach.