How to implement Array.prototype.every? JavaScript Interview Question | Problem Solving | JavaScript Polyfills
In this question, the candidate needs to implement a function customEvery
that mimics the behaviour of Array.prototype.every
method.
More about Array.prototype.every
The every() method tests whether all elements in the array pass the test implemented by the provided function. It returns a Boolean value.
Examples
const even = (element) => element % 2 === 0;
const array = [2, 4, 6, 8];
// expected output: true
console.print(array.every(even));
Syntax
The customEvery
takes two parameters
callback
function
Function to execute on each value in the array. The function is called with the following arguments:
element
- The current element in the array.
index
- The index (position) of the current element in the array.
array
- The array that
customFind
was called on.
The callback must return a truthy value to indicate a matching element has been found.
thisArg
(Optional)
Object to use as this
inside callbackFn.
const input = [2,4,6,8];
const event = (element) => element % 2 === 0;
// customEvery(callback, thisArg)
customEvery(even, input);
Return Value
true
if the callbackFn function returns a truthy value for every array element. Otherwise, false
.
Submission
Start the timer, complete your solution, and test it against the test cases provided by the platform. Ideally, you should finish this question within 15 mins. Share your solution with us -- https://twitter.com/devtoolstech