🔲 Array.prototype.fill() Polyfill

The fill() method changes all elements in an array to a static value, from a start index to an end index.

✅ Implementation

Array.prototype.customFill = function(value, start = 0, end = this.length) {
    // Adjust negative indices for start and end
    start = start < 0 ? Math.max(this.length + start, 0) : start;
    end = end < 0 ? Math.max(this.length + end, 0) : end;

    // Fill the array with the given value from start to end (end is exclusive)
    for (let i = start; i < end; i++) {
        this[i] = value;
    }

    return this; // Return the modified array since fill modifies it in place
};

// Example usage:
const array1 = [1, 2, 3, 4];

console.log(array1.customFill(0, 2, 4)); // Output: [1, 2, 0, 0]
console.log(array1.customFill(5, 1));    // Output: [1, 5, 5, 5]
console.log(array1.customFill(6));       // Output: [6, 6, 6, 6]

How It Works:

• Parameters :
• value: The value to fill the array with.
• start: The index to begin filling from (defaults to 0).
• end: The index to stop filling at (non-inclusive, defaults to the array’s length).
• Negative Indices : If start or end are negative, they are adjusted to count from the end of the array.
• Filling the Array : A for loop iterates from start to end (not including end) and fills the array with value.
• In-Place Modification : Since .fill() modifies the array directly, customFill returns the modified array.

Key Features:

• Supports negative indices by adjusting them to count from the end of the array.
• Modifies the array in place and returns the updated array reference (like .fill()).
• Defaults to start = 0 and end = array.length if not provided.