I am solving the following leetcode question and have the solution below
const twoSum = (numbers, target) => {
let map = {}
let result = []
for (let i = 0; i < numbers.length; i++) {
let complement = target - numbers[i]
if (map[complement] === undefined) {
map[numbers[i]] = i
} else {
result[0] = map[complement] + 1
result[1] = i + 1
}
}
return result
};
If I replace map[complement] === undefined with !map[complement] I return an empty array. In my mind both should return true. Why does the latter breaks my code?
map[complement] === undefined only becomes true when there is no element with the key equal to complement while !map[complement] becomes true in all the cases where its result is a falsy value.
Falsy values include but are not limited to, "", false, undefined, null, 0, -0, etc.
In other words, the first case is a sub set of the second.