JavaScript Array Series – Creating Own push() Method

In my previous blogs, I explained how the JavaScript length property works and also created my own version of the toString() method without using JavaScript's built-in methods.

Today, I continued this learning journey by creating my own version of another important array method: push().

Instead of using JavaScript's built-in push() method, I tried to understand how it works internally by implementing it manually.

What is push() Method?

The push() method is used to add a new element at the end of an array.

Example:

const arr = [1, 2, 3];

arr.push(4);

console.log(arr); // [1, 2, 3, 4]

In this blog, I did not use the built-in push() method. Instead, I created my own logic.

My Approach

const arr = [1, , 3, 4, 5];
let user = "gunalan";

arr[countOfLength()] = user;

function countOfLength() {
    let lengthDemo = 0;

    for (let count of arr) {
        lengthDemo++;
    }

    return lengthDemo;
}

console.log(arr);

How Does This Work?

Step 1: Create an Array and a New Value

const arr = [1, , 3, 4, 5];
let user = "gunalan";

Here, I created an array and a new value that needs to be added.

Step 2: Find the Length of the Array

function countOfLength() {
    let lengthDemo = 0;

    for (let count of arr) {
        lengthDemo++;
    }

    return lengthDemo;
}

I created a custom function called countOfLength().

Inside this function:

I started a variable named lengthDemo with value 0. Then I used a for...of loop to visit every element in the array.
For each iteration, I increased lengthDemo by 1.
Finally, I returned the total count.

Step 3: Add the New Value

arr[countOfLength()] = user;

After finding the length, I used that value as the new index.

For example, if the array length is 5, the new value will be added at index 5.

This is similar to how the original push() method works.

Output:

[1, empty, 3, 4, 5, "gunalan"]

What I Learned

By creating this custom push() method, I learned:

✅ How the push() method adds values to an array.

✅ How array indexes work internally.

✅ How to create custom functions.

✅ How loops can be used to recreate built-in methods.

Conclusion

• Implementing JavaScript methods manually is one of the best ways to understand how JavaScript works behind the scenes.
• Every day, I am trying to recreate built-in methods step by step. This process is helping me improve my JavaScript fundamentals and problem-solving skills.
• I will continue this series by implementing more JavaScript methods

Stay tuned for the next blog! 👋