findTwoNumbers.js

function twoNumberSum(array, targetSum) {
	if ( !Array.isArray(array) || !array.length ) throw new Error('You must provide an array of values.');
	const result = [];
	const numberMap = {};
	
	for ( let i = 0; i < array.length; i++ ) {
		const diff = targetSum - array[i];
		console.log(diff)
		if ( numberMap[diff] ) {
			result.push(array[i], diff);
			break;
		}
		numberMap[array[i]] = true;
	}
	
	return result;
}