Job Interview Question about to find an algorithm and performance for a certain situation

interview-algorithm-performance.js

/**
 * This are your TODOs:
 *
 * Given is a list of random integers inside of an array. You have to implement
 * a JavaScript function which finds the first pair of entries which summ up to
 * the given integer value.
 *
 * Example: 
 * - sum should be 8
 * - example arrays are: a = [ 1, 2, 3, 9 ]   b = [ 1, 2, 4, 4 ]
 *
 * Please design your function with efficiency in mind.
 */