sorting of array manually in javascript

Question

I have an array of strings like below.

ABC
QRS
DEF
HIJ
TUV
KLM
NOP

I need to sort this array in javascript in alphabetical order, except for few values which is already known. ie I need DEF and NOP comes in the first 2 positions and sort rest of the array alphabetically in ascending order. Here is what I've written to sort the entire array in alphabetical order, now I need the 2 values in the first 2 positions.

array.sort(function(a,b){return ((a < b) ? -1 : (a > b) ? 1 : 0)});

Expected result.

DEF
NOP
ABC
HIJ
KLM
QRS
TUV

The contents of the array is dynamic, so if the array has DEF or NOP, then those should be on top, if else, it should be sorted alphabetically. Whats the best way to approach this?

Ry- · Accepted Answer · 2015-04-21 18:47:24Z

5

I think the most straightforward way would be to remove the known elements separately instead of trying to incorporate them into the sort. That way, you can also just sort without a comparison function.

function sortWithKnownPrefix(prefix, arr) {
    // Get the non-prefix elements
    var rest = arr.filter(function (item) {
        return prefix.indexOf(item) === -1;
    });

    // Concatenate the prefix and the sorted non-prefix elements
    return prefix.concat(rest.sort());
}

sortWithKnownPrefix(
    ["DEF", "NOP"],
    ["ABC", "QRS", "DEF", "HIJ", "TUV", "KLM", "NOP"]
)
// ["DEF", "NOP", "ABC", "HIJ", "KLM", "QRS", "TUV"]

answered Apr 21, 2015 at 18:47

Ry-♦

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Comments

Sidd · Accepted Answer · 2015-04-21 18:52:57Z

0

If you want to allow for, count and hoist multiple instances of those strings: http://jsfiddle.net/4hgnjqas/1/

The following will count all known instances of the strings you want to hoist to the front, remove them from the existing array, sort it, then add the same number of "DEF"s and "NOP"s to the array.

var hoist = {"NOP":0, "DEF":0}

for(var p in hoist)
    while(array.indexOf(p)>-1){
        array.splice(array.indexOf(p),1);
        hoist[p]++;
    }
arr.sort();
for(var p in hoist){
    for(var i=0;i<hoist[p];i++)
        array.unshift(p);
}
console.log(array);

answered Apr 21, 2015 at 18:52

Sidd

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Comments

djfdev · Accepted Answer · 2015-04-21 19:07:49Z

0

This will reposition 'DEF' and 'NOP' after sorting the rest of the items:

function customSort(array) {

  array  = array.sort(function(a,b){
    return (a < b) ? -1 : (a > b) ? 1 : 0;
  });

  var NOPIndex = array.indexOf('NOP');
  if (NOPIndex > -1)
    array.unshift(array.splice(NOPIndex, 1)[0]);

  var DEFIndex = array.indexOf('DEF');
  if (DEFIndex > -1)
    array.unshift(array.splice(DEFIndex, 1)[0]);

  return array;

}

answered Apr 21, 2015 at 19:07

djfdev

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Comments

Ja9ad335h · Accepted Answer · 2015-04-21 19:22:07Z

0

this could be the simpler one

var arr = ['ABC','QRS','DEF','HIJ','TUV','KLM','NOP']
var exclude = ['DEF', 'NOP'];

arr.sort(function(a,b) {
    if(exclude.indexOf(a) > -1 && exclude.indexOf(b) > -1)
        return ((a < b) ? -1 : (a > b) ? 1 : 0);
    if(exclude.indexOf(b) > -1) 
        return 1;
    return ((a < b) ? -1 : (a > b) ? 1 : 0)
});

alert(JSON.stringify(arr))  //result

JS Fiddle *UPDATED

edited Apr 21, 2015 at 19:22

answered Apr 21, 2015 at 18:54

Ja9ad335h

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2 Comments

Sidd Over a year ago

Nice, except the order of 'DEF' and 'NOP' is reversed.

jijo Over a year ago

This looks good, but I need to maintain the order of exclude array in the result array..

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