Return Largest Number in Arrays

JavaScript
#1

Tell us what’s happening:

Can return ‘ar’ and ‘len’ right but returns nothing for ‘arg’. The syntax seems right and it’s no runtime error. I don’t understand why ‘len’ isn’t ‘pushed’ to ‘arg’.

Your code so far


function largestOfFour(ar) {
  	var arg = []; //to put the numbers in
  	var len = ar.length; //how many miniarrays there are
  	for(var x = 0; i<len; i++){ //loops the number of miniarrays
  		var lar = 0; //to store the biggest int of four
  		lar = ar[0]; //lar = firstnum of miniarray
		for(var i = 0; i<4; i++){ //four times (i = 0,1,2,3)
  			if(ar[i]>lar){lar=ar[i];} //sets lar equal if(i[1/2/3] are bigger than ar[0])
  		}
  		arg.push(lar);//pushes biggest num on arg
  	}
  	return arg; //returns arg
}

largestOfFour([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [1000, 1001, 857, 1]]);

Your browser information:

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36.

Link to the challenge:
https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-algorithm-scripting/return-largest-numbers-in-arrays

1 Like
#2

First problem is your for loop condition of i < len above. The variable i you are comparing to len is undefined when the for loop starts, so you are comparing undefined < len which evaluates to false, so the outer for loop never executes and all you do is return arg which is an empty array.

Next problem if you figure out what to put for the initial value and the condition expression of the outer for loop, is the line above. Think about what kind of value ar[i] is. Since ar is an array containing elements which are arrays, then ar[i] is an array, so your comparison to lar will always evaluate to false, so the lar=ar[i] will never execute.

#4

With what could I compare it instead? And thx for your answer

#5

Try using the Math.max and Math.min functions., here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/max

#6

It worked, thanks :smile:

function largestOfFour(ar) {
  	var arg = []; //to put the numbers in
  	var len = ar.length; //how many miniarrays there are
  	for(var i = 0; i<len; i++){ //loops the number of miniarrays
  		var lar = 0; //to store the biggest int of four
  		lar = ar[0]; //lar = firstnum of miniarray
		lar = Math.max(...ar[i]); //to find the highest value of the four
  		arg.push(lar);//pushes biggest num on arg
  	}
  	return arg; //returns arg
}
#7

Or you can just return Math.max (…arr);

function largestOfFour (arr){
    return Math.max (...arr);
}
#8