Problem

Given a function fn, return a new function that is identical to the original function except that it ensures fn is called at most once.

The first time the returned function is called, it should return the same result as fn. Every subsequent time it is called, it should return undefined.

Example 1:

Input: fn = (a,b,c) => (a + b + c), calls = [[1,2,3],[2,3,6]] Output: [{“calls”:1,”value”:6}] Explanation: const onceFn = once(fn); onceFn(1, 2, 3); // 6 onceFn(2, 3, 6); // undefined, fn was not called

Example 2:

Input: fn = (a,b,c) => (a _ b _ c), calls = [[5,7,4],[2,3,6],[4,6,8]] Output: [{“calls”:1,”value”:140}] Explanation: const onceFn = once(fn); onceFn(5, 7, 4); // 140 onceFn(2, 3, 6); // undefined, fn was not called onceFn(4, 6, 8); // undefined, fn was not called

Constraints:

calls is a valid JSON array 1 <= calls.length <= 10 1 <= calls[i].length <= 100 2 <= JSON.stringify(calls).length <= 1000

Pre analysis

Will just keep a lock variable to check if function is called or not.