// For regular arrays:
var max = Math.max(...arrayOfNumbers);
// For arrays with tens of thousands of items:
let max = testArray[0]; //here we have considered max to the first element because we don't know which is max yet.
for (let i = 1; i < testArrayLength; ++i) {
if (testArray[i] > max) { //in each iteration it will compare if the value is greater than the current considered value (we just considered first element)
max = testArray[i]; //in the above iteration if the testArray find value/element greater than max then this new max value will be considered as Max (this will happen until the max value found).
}
}