Javascript find max number from 3 inputs

Question

I've just began Javascript in college. One task is to define and call a function to find the maximum number from 3 numbers entered by the user. I know there is a max() function but we were told to do it manually using if and else if.

I'm going wrong somewhere as you can see. It's just telling me the max is 0 everytime.

function maxNum(num1, num2, num3){
        var max = 0;
        if(num1 > num2){
            if(num1 > num3){
                num1 = max;
            }
            else{
                num3 = max;
            }
        }
        else{
            if(num2 > num3){
                num2 = max;
            }
        }
    return max;
    }

    for(i=0;i<3;i++){
        parseInt(prompt("Enter a number"));
    }
    document.write(maxNum());

Answer 1

Or you can use ES6 syntax, to compute largest of three numbers in easier way,

const largest = a => F = b => G = c => ((a > b && a > c) ? a : (b > a && b > c) ? b : c)

console.time()
console.log(largest(53)(30907)(23333))
console.timeEnd()

Answer 2

One problem you have is that you do not save the number the user inputs. You prompt them, parse it as an int and then nothing. You have to pass the 3 numbers into maxNum()

Here is a working example that uses proper left hand assignment and saves the number. Also it is a good idea to use >= instead of > because the user can enter 2 of the same number

function maxNum(num1, num2, num3){
        var max = 0;
        if((num1 >= num2) && (num1 >= num3)){
            max = num1;
        }
        else if((num2 >= num1) && (num2 >= num3)){
            max = num2;
        }
        else{
            max = num3;
        }
    return max;
    }

    var arr = []; 
    for(i=0;i<3;i++){
        arr[i] = parseInt(prompt("Enter a number"));
    }


    document.write(maxNum.apply(this, arr));