JavaScript findMax（）示例-需要说明

Question

I'm going through a W3Schools tutorial on JavaScript and I was just wondering about this findMax() function:

function findMax() {
    var i;
    var max = -Infinity;
    for (i = 0, i < arguments.length; i++) {
        if (arguments[i] > max) {
            max = arguments[i];
        }
    }
    return max;
}

I understand that 'i' is a counter, the function goes until everything has been counted, and the count is increased by 1. What I don't understand - how does creating an if statement (arguments[i] > max) ... get the highest number in the findMax() function? Why does passing i into the if statement give the max number back?

Answer 1

In that particular line of code, the loop is checking each value with the arguments array to see if it higher than the currently highest value saved in max . If it is not, then it moves on to the next one. If it is, then it changes max to the new highest value. Once the loop has checked each value in the arguments array, then the function returns the highest value ( max ).

Answer 2

The if statement doesn't look directly at the value of i. Instead, it is used as an index to a specific value in the array arguments .
Each time you find a value higher than all values you already saw, it means this is the new maximum.

Answer 3

You seem to be thinking that max is being compared to i . That's not the case. i is being used to loop through the elements of arguments .

Lets say that you call findMax like this findMax(1, 2, 3, 4, 5) . Then arguments is equal to [1, 2, 3, 4, 5] .

What happens then is that your for loop will iterate through each of the elements of arguments .

• if (arguments[0] > max) is the same as Is 1 > -Infinity? (yes)
• if (arguments[1] > max) is the same as Is 2 > 1? (yes)
• if (arguments[2] > max) is the same as Is 3 > 2? (yes)
• if (arguments[3] > max) is the same as Is 4 > 3? (yes)
• if (arguments[4] > max) is the same as Is 5 > 4? (yes)

Which gives you 5 as the max.