Google - pairs for sum
JavaScript
function pairForSum(array, sum) {
let seenNumbers = [];
for (let i = 0; i < array.length; i++) {
let complement = sum - array[i];
if (complement <= 0) continue;
if (seenNumbers.indexOf(complement) == -1) {
seenNumbers.push(array[i]);
} else {
console.log(complement, array[i]);
}
}
}
console.log(pairForSum([1,7,5,2,3,4,5,8], 10));