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I have an array with different values in it and I'd like to sort it by the numeric value in one of the indexes 

const arr = [
  ['foo', var, 5],
  ['fee', var, 7],
  ['faa', var, 3]
]

I want to sort this array from big to small using arr[2] value. Any idea how it can be done?

the desire outcome should be: 

const arr = [
  ['fee', var, 7],
  ['foo', var, 5],
  ['faa', var, 3]      
]
obiwankenoobi
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2 Answers2

2

You can use sort like this:

arr.sort((a,b) => {
  return a[2] < b[2] // To sort in descending order
  // return a[2] > b[2] // To sort in ascending order
})

Example:

var arr = [
  ['foo', 'fifth', 5],
  ['fee', 'seventh', 7],
  ['faa', 'third', 3]
];

var sortedArr = arr.sort(function(a,b){
  return a[2] < b[2]
});

console.log(sortedArr)

Here's how sort function work

First, let's assume this array:

[1,2] // where a = 1, b = 2

Ascending order:

Is a greater than b?

If it is yes, we need to sort => return true

Else, we don't need to sort => return false

Descending order:

Is a lesser than b?

If it is yes, we need to sort => return true

Else, we don't need to sort => return false

In preceding example, we're verifying if a is lesser than b, then return true to sort it out else return false as this is already in descending order.

As per @Nina Scholz

Please do not return a Boolean value for sorting, because sort needs a value smaller than zero, zero or greater than zero. To omit equal cases may actually work, but it make for the algorithm harder to get the array to sort.

You should consider returning 0, 1, or -1. For your case, you should use like this:

arr.sort((a,b) => {
  if(a[2] < b[2]) return 1
  if(a[2] > b[2]) return -1
  if(a[2] === b[2]) return 0
})

Furthermore

If the values are only integers (doesn't contain Infinity and NaN), then it can be simplifies as below,

arr.sort((a,b) => b[2]-a[2])
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Bhojendra Rauniyar
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  • please do not return a boolean value for sorting, because sort needs a value smaller than zero, zeor or greater than zero. to omit equal cases may actually work, but it make for the algorithm harder to get the array to sort. – Nina Scholz Jun 16 '18 at 19:03
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    should be `arr.sort((a,b) => b[2] - a[2])`. see https://stackoverflow.com/questions/24080785/sorting-in-javascript-shouldnt-returning-a-boolean-be-enough-for-a-comparison – Slai Jun 16 '18 at 19:11
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function bubbleSort(arr){
   var len = arr.length;
   for (var i = len-1; i>=0; i--){
     for(var j = 1; j<=i; j++){
       if(arr[j-1]<arr[j]){
           var temp = arr[j-1];
           arr[j-1] = arr[j];
           arr[j] = temp;
        }
     }
   }
   return arr;
}

console.log( bubbleSort([7,5,2,4,3,9]))

console.log out put is 9 7 5 4 3 2 Modify the code to loop through your object.var in Array

Marcia Ong
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