Program to test the equality of two arrays - JavaScript

We are required to write a JavaScript function that takes in two arrays of literals and checks the corresponding elements of the array and it should return true if all the corresponding elements of the array are equal otherwise it should return false.

Let's write the code for this function ?

Example

Following is the code ?

const arr1 = [1, 4, 5, 3, 5, 6];
const arr2 = [1, 4, 5, 2, 5, 6];

const areEqual = (first, second) => {
    if(first.length !== second.length){
        return false;
    };
    for(let i = 0; i < first.length; i++){
        if(first[i] === second[i]){
            continue;
        }
        return false;
    };
    return true;
};

console.log(areEqual(arr1, arr2));

Output

Following is the output in the console ?

false

Method 1: Using for loop (Optimized)

We can simplify the logic by directly returning false when elements don't match:

const arr1 = [1, 2, 3, 4];
const arr2 = [1, 2, 3, 4];

const areEqual = (first, second) => {
    if(first.length !== second.length){
        return false;
    }
    
    for(let i = 0; i < first.length; i++){
        if(first[i] !== second[i]){
            return false;
        }
    }
    
    return true;
};

console.log(areEqual(arr1, arr2));
console.log(areEqual([1, 2, 3], [1, 2, 4]));

true
false

Method 2: Using every() Method

The every() method provides a more functional approach:

const areEqual = (first, second) => {
    return first.length === second.length && 
           first.every((element, index) => element === second[index]);
};

console.log(areEqual([1, 2, 3], [1, 2, 3]));
console.log(areEqual([1, 2, 3], [1, 2]));
console.log(areEqual(['a', 'b'], ['a', 'c']));

true
false
false

Method 3: Using JSON.stringify() (Simple Arrays Only)

For arrays containing only primitive values, JSON comparison works:

const areEqual = (first, second) => {
    return JSON.stringify(first) === JSON.stringify(second);
};

console.log(areEqual([1, 2, 3], [1, 2, 3]));
console.log(areEqual(['x', 'y'], ['x', 'z']));
console.log(areEqual([1, 2], [2, 1])); // Order matters

true
false
false

Comparison

Key Points

• Always check array lengths first for performance
• Use strict equality (===) to avoid type coercion
• The every() method is most readable for functional programming
• JSON.stringify() works for nested arrays but is slower

Conclusion

The for loop approach offers the best performance for simple array comparison. Use every() for cleaner, more readable code in functional programming style.