Why -Infinity is like a base for comparing numbers to return max?

Question

In this code i can't seem to understand why -Infinity is behaving like a base so when compared to it returns the biggest number from an array of numbers.

function max(...numbers) {
   let result = -Infinity;
   for (let number of numbers) {
     if (number > result) result = number;
   }
   return result;
}

Answer 1

It is confusing at first and probably in your mind a solution would sound like this:

 let result = 0;

The problem is that when we want to find the MAXIMUM value of an array we need to compare every element with each other. It is more like a "habit" that we set the MAXIMUM to -INFINITY. That simply means that the biggest element so far is the lowest possible number that we can express. Does it make sense? We simply assume that the biggest number we will every find is -Infinity. Then we compare the elements from the array with this base number(in our case -Infinity) and if we were false (and probably we were) then we replace -Infinity with the next number that's bigger than our current value. We do that for the whole range of numbers and that's how we find the Maximum element.

You can pick multiple elements as the starting point, but never pick a number entered by yourself( you should do that ONLY if the exercise asks so). If you would pick for example:

let result = 0;

then you might have a problem. Maybe the numbers are all negative, for example [-3,-13,-5,13,-99] but you already set the biggest number to 0 so every comparation would be wrong and useless.

So, keep in mind that is a good practice, in this case, to set the base value to -Infinity or if you would like to take another approach then set the base value to the first element in the array.