JavaScript method not properly sorting the last nested array

Question

JavaScript method not properly sorting the last nested array

I am having trouble with sorting the last nested array using arr[i].sort(). Despite trying various methods such as FOR and WHILE loops along with different operators, I still cannot achieve the desired result. Can someone help me identify what I am doing wrong? The goal is to return the largest numbers in the arrays.

function findLargestNumbers(arr) {
  var i = 0;
  while (i != arr.length) {
    arr[i] = arr[i].sort().pop();
    i++;
  }
  return arr;
}

findLargestNumbers([
  [4, 5, 8, 1, 3],
  [13, 27, 18, 26],
  [32, 35, 37, 39],
  [1000, 1001, 817, 1]
]);

javascript arrays sorting methods

Answer 1

Answer №1

By default, when using the sort() method, the elements are ordered as strings instead of numbers. This can lead to unexpected results, such as "1001" < "817". To achieve a numeric sort, a comparison function that performs numerical ordering needs to be provided.

function findLargestNumber(arr) {
  var i = 0;
  while (i != arr.length) {
    arr[i] = arr[i].sort(function(a, b) {
        return a - b;
    }).pop();
    i++;
  }
  return arr;
}

console.log(findLargestNumber([
  [4, 5, 8, 1, 3],
  [13, 27, 18, 26],
  [32, 35, 37, 39],
  [1000, 1001, 817, 1]
]));

Answer 2

By default, when using the sort() method, the elements are ordered as strings instead of numbers. This can lead to unexpected results, such as "1001" < "817". To achieve a numeric sort, a comparison function that performs numerical ordering needs to be provided.

function findLargestNumber(arr) {
  var i = 0;
  while (i != arr.length) {
    arr[i] = arr[i].sort(function(a, b) {
        return a - b;
    }).pop();
    i++;
  }
  return arr;
}

console.log(findLargestNumber([
  [4, 5, 8, 1, 3],
  [13, 27, 18, 26],
  [32, 35, 37, 39],
  [1000, 1001, 817, 1]
]));

Answer 3

Answer №2

Although not the root cause of the issue you are encountering (as answered by @Barmar), an alternative method is using Array.map in combination with Math.max.apply to determine the maximum number in each list:

function largestOfFour(arr) {
   return arr.map(function(list) {
      return Math.max.apply(null, list);
   });
}

console.log(largestOfFour([
  [4, 5, 8, 1, 3],
  [13, 27, 18, 26],
  [32, 35, 37, 39],
  [1000, 1001, 817, 1]
]));

An even more concise approach utilizing ES6:

const largestOfFour = arr => arr.map(list => Math.max(...list))

Answer 4

Although not the root cause of the issue you are encountering (as answered by @Barmar), an alternative method is using Array.map in combination with Math.max.apply to determine the maximum number in each list:

function largestOfFour(arr) {
   return arr.map(function(list) {
      return Math.max.apply(null, list);
   });
}

console.log(largestOfFour([
  [4, 5, 8, 1, 3],
  [13, 27, 18, 26],
  [32, 35, 37, 39],
  [1000, 1001, 817, 1]
]));

An even more concise approach utilizing ES6:

const largestOfFour = arr => arr.map(list => Math.max(...list))

Answer 5

Answer №3

The issue lies in the default sorting method which treats numbers as strings - causing "8..." to be greater than "1...".

One potential solution is to implement a custom comparison function:

function cmp(a,b){
  return a-b;
}

function getLargestNumbers(arr) {
  var i = 0;
  while (i != arr.length) {
    arr[i] = arr[i].sort(cmp).pop();
    i++;
  }
  return arr;
}

getLargestNumbers([
  [4, 5, 8, 1, 3],
  [13, 27, 18, 26],
  [32, 35, 37, 39],
  [1000, 1001, 817, 1]
]);

Expected Output: [ 8, 27, 39, 1001 ]

Answer 6

The issue lies in the default sorting method which treats numbers as strings - causing "8..." to be greater than "1...".

One potential solution is to implement a custom comparison function:

function cmp(a,b){
  return a-b;
}

function getLargestNumbers(arr) {
  var i = 0;
  while (i != arr.length) {
    arr[i] = arr[i].sort(cmp).pop();
    i++;
  }
  return arr;
}

getLargestNumbers([
  [4, 5, 8, 1, 3],
  [13, 27, 18, 26],
  [32, 35, 37, 39],
  [1000, 1001, 817, 1]
]);

Expected Output: [ 8, 27, 39, 1001 ]

JavaScript method not properly sorting the last nested array

Answer №1

Answer №2

Answer №3

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