What arguments should the map callback receive in a polyfill?
Three arguments: the current element, the current index, and the array itself. Use callback.call(thisArg, this[i], i, this) to support the optional thisArg parameter.
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More FAQs in Other Polyfills to Practice for Interviews
Loop through the array, call the callback with (element, index, array), push the result to a new array, return it. Use let in the loop and do not mutate the original.
Handle the initial value: if provided, start with it at index 0; if not, use the first element at index 1. Throw TypeError for empty arrays without initial value. Loop and update the accumulator.
Return a new Promise. Track completed count. For each promise, resolve and store the result at its index. When all complete, resolve with the results array. If any rejects, reject immediately.
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