🔘 Array.prototype.some() Polyfill

jspolyfillsmedium

The some() method tests whether at least one element in the array passes the test implemented by the provided function.

✅ Implementation

Array.prototype.customSome = function (callback, thisArg) {
    if (typeof callback !== 'function') {
        throw new TypeError(callback + ' is not a function');
    }

    for (let i = 0; i < this.length; i++) {
        if (callback.call(thisArg, this[i], i, this)) {
            return true; // Return true immediately if a match is found
        }
    }

    return false; // Return false if no element satisfies the condition
};

// Example usage:
const array = [1, 2, 3, 4, 5];

const even = (element) => element % 2 === 0;

console.log(array.customSome(even)); // Output: true
console.log(array.customSome((num) => num > 10)); // Output: false

How This Works

Checks if callback is a function
- If not, it throws a TypeError (same behavior as Array.prototype.some).
Iterates through the array
- Calls callback for each element with (element, index, array).
- Uses .call(thisArg, ...) to bind the optional thisArg.
Returns early if a match is found
- If callback returns true, customSome immediately returns true.
Returns false if no match is found
- If no element passes the test, customSome returns false after the loop.

Edge Cases Handled

✔ Empty array always returns false

✔ Works with thisArg binding

✔ Stops checking as soon as one match is found (Optimized)

✔ Throws an error if callback is not a function

This version is simple, efficient, and follows the behavior of Array.prototype.some exactly.

Quick Quiz

Test your understanding with 3 quick questions

Q1What does `[].customSome(x => x > 0)` return?

Q2When does `some()` return `true`?

Q3What is the key difference between `some()` and `every()`?

🔘 Array.prototype.some() Polyfill

jspolyfillsmedium

The some() method tests whether at least one element in the array passes the test implemented by the provided function.

✅ Implementation

Array.prototype.customSome = function (callback, thisArg) {
    if (typeof callback !== 'function') {
        throw new TypeError(callback + ' is not a function');
    }

    for (let i = 0; i < this.length; i++) {
        if (callback.call(thisArg, this[i], i, this)) {
            return true; // Return true immediately if a match is found
        }
    }

    return false; // Return false if no element satisfies the condition
};

// Example usage:
const array = [1, 2, 3, 4, 5];

const even = (element) => element % 2 === 0;

console.log(array.customSome(even)); // Output: true
console.log(array.customSome((num) => num > 10)); // Output: false

How This Works

Checks if callback is a function
- If not, it throws a TypeError (same behavior as Array.prototype.some).
Iterates through the array
- Calls callback for each element with (element, index, array).
- Uses .call(thisArg, ...) to bind the optional thisArg.
Returns early if a match is found
- If callback returns true, customSome immediately returns true.
Returns false if no match is found
- If no element passes the test, customSome returns false after the loop.

Edge Cases Handled

✔ Empty array always returns false

✔ Works with thisArg binding

✔ Stops checking as soon as one match is found (Optimized)

✔ Throws an error if callback is not a function

This version is simple, efficient, and follows the behavior of Array.prototype.some exactly.

Quick Quiz

Test your understanding with 3 quick questions

Q1What does `[].customSome(x => x > 0)` return?

Q2When does `some()` return `true`?

Q3What is the key difference between `some()` and `every()`?

🔘 Array.prototype.some() Polyfill

✅ Implementation

How This Works

Edge Cases Handled

Continue Reading

🛑 AbortController: Canceling Async Operations in JavaScript

🔒 Closures in JavaScript — The Complete Guide

📦 Understanding ES6 Modules in JavaScript

🔘 Array.prototype.some() Polyfill

✅ Implementation

How This Works

Edge Cases Handled

Continue Reading

🛑 AbortController: Canceling Async Operations in JavaScript

🔒 Closures in JavaScript — The Complete Guide

📦 Understanding ES6 Modules in JavaScript