While loop stops at first iteration

Question

I'm trying to add all the numbers for matching arrays and remove the duplicate names. It works for the first instance, but the while loop won't go past Apples.

function updateInventory(arr1, arr2) { function alphabetizer(a, b) { if (a[1] < b[1]) return -1; if (a[1] > b[1]) return 1; return 0; } var newInv = arr1.concat(arr2).sort(alphabetizer); for(i=0;i<newInv.length;i++){ while(newInv[i][1] != -1){ newInv[i][0] += newInv[i+1][0]; newInv.push([newInv[i][0], newInv[i][1]]); newInv.splice(i,2); return newInv; } return newInv; } return newInv; } // Example inventory lists var curInv = [ [21, "Bowling Ball"], [2, "Dirty Sock"], [1, "Hair Pin"], [5, "Microphone"], [10, "Apples"] ]; var newInv = [ [9, "Apples"], [2, "Hair Pin"], [3, "Half-Eaten Apple"], [67, "Bowling Ball"], [7, "Toothpaste"] ]; updateInventory(curInv, newInv);

So when I run this I just end up getting

[[21,"Bowling Ball"],[67,"Bowling Ball"],[2,"Dirty Sock"],[1,"Hair Pin"],[2,"Hair Pin"],[3,"Half-Eaten Apple"],[5,"Microphone"],[7,"Toothpaste"],[19,"Apples"]]

Suren Srapyan · Accepted Answer · 2017-11-22 09:40:27Z

3

The problem is because you are returning from the while loop. It terminates the further execution of the loop. Remove return part from the for and while loops. And also declare variable i with var keyword to make it scoped to the function, not global.

for(var i = 0; i < newInv.length; i++) { while(newInv[i][1] != -1) { newInv[i][0] += newInv[i+1][0]; newInv.push([newInv[i][0], newInv[i][1]]); newInv.splice(i,2); } }

answered Nov 22, 2017 at 9:40

Suren Srapyan

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7 Comments

Cody Over a year ago

I did it like this, but was getting 'TypeError: newInv[i] is undefined' even after adding the 'var' which is what I think I was missing earlier. Adding in the return gets rid of this error.

Suren Srapyan Over a year ago

It can not be related to the return. Your return just terminates the function

Cody Over a year ago

I didn't think so. I was just pointing out that it does not throw that error WHEN i have the return in there.

Suren Srapyan Over a year ago

Maybe when an item except the first has undefined, so when you have return it does not reach to that element, but when you remove it iterates and reaches

Cody Over a year ago

I'm a bit confused then, since its saying the newInv[i + 1] is not defined. But if I change it to newInv[i++] it says newInv[i] meaning the one before it, is undefined. So I'm not sure why it would be saying that either of those are undefined, since i is declared right before it at a var.

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Cody · Accepted Answer · 2017-11-23 15:35:21Z

This got it working, adding var j = i and changing some code.

function updateInventory(arr1, arr2) { function alphabetizer(a, b) { if (a[1] < b[1]) return -1; if (a[1] > b[1]) return 1; return 0; } var newInv = arr1.concat(arr2).sort(alphabetizer); for (var i = 0; i < newInv.length; i++) { var j = i; while (newInv[j + 1] && newInv[j][1] == newInv[j + 1][1]) { newInv[j][0] += newInv[j + 1][0]; newInv.splice(j + 1, 1); j++; } } document.getElementById('test').innerHTML = newInv.join('<br>'); } // Example inventory lists var curInv = [ [21, "Bowling Ball"], [2, "Dirty Sock"], [1, "Hair Pin"], [5, "Microphone"], [10, "Apples"] ]; var newInv = [ [9, "Apples"], [2, "Hair Pin"], [3, "Half-Eaten Apple"], [67, "Bowling Ball"], [7, "Toothpaste"] ]; updateInventory(curInv, newInv);

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