javascript - Sort Array by occurrence of its elements - Stack Overflow

admin管理员组

文章数量:1253740

I'm looking for an elegant way of sorting an array by the occurrence of its elements.

For example, in:

['pear', 'apple', 'orange', 'apple', 'orange', 'apple']

the output should look like

['apple', 'orange', 'pear']

I have tried to loop through the array and save the occurrence in another temporary array, but this solution was quite bad.

I'm looking for an elegant way of sorting an array by the occurrence of its elements.

For example, in:

['pear', 'apple', 'orange', 'apple', 'orange', 'apple']

the output should look like

['apple', 'orange', 'pear']

I have tried to loop through the array and save the occurrence in another temporary array, but this solution was quite bad.

• javascript
• arrays

Share Improve this question Follow edited Dec 21, 2015 at 13:53 T J 43.2k1313 gold badges8686 silver badges142142 bronze badges asked Dec 21, 2015 at 13:23 Carle B. NavyCarle B. Navy 1,16611 gold badge1111 silver badges2929 bronze badges 2

• You have to loop through . without looping in you can't – Ashisha Nautiyal Commented Dec 21, 2015 at 13:26
• 4 Why was your solution bad? Can you post it? – abl Commented Dec 21, 2015 at 13:27

Add a ment  | 

7 Answers 7

Sorted by: Reset to default 10

It would require two loops.

    var arr = ['pear', 'apple', 'orange', 'apple', 'orange', 'apple'];
    //find the counts using reduce
    var cnts = arr.reduce( function (obj, val) {
        obj[val] = (obj[val] || 0) + 1;
        return obj;
    }, {} );
    //Use the keys of the object to get all the values of the array
    //and sort those keys by their counts
    var sorted = Object.keys(cnts).sort( function(a,b) {
        return cnts[b] - cnts[a];
    });
    console.log(sorted);

Map the values into a fruit→count associated object:

var counted = fruits.reduce(function (acc, fruit) {
    if (acc[fruit]) {
        acc[fruit]++;
    } else {
        acc[fruit] = 1;
    }
    return acc;
}, {});

Map that object into a sortable array:

var assoc = counted.keys().map(function (fruit) {
    return [fruit, counted[fruit]];
});

Sort the array:

assoc.sort(function (a, b) { return a[1] - b[1]; });

Extract the values:

var result = assoc.map(function (i) { return i[0]; });

You can reduce your array to remove duplicates and then sort with custom parator:

var sorted = ['pear', 'apple', 'orange', 'apple', 'orange', 'apple'].reduce(function(result, item) {
    result.every(function(i) {
        return i != item;
    }) && result.push(item);
    return result;
}, []).sort(function(i1, i2) {
    return i1 > i2;
});
console.log(sorted);

With linq.js it is pretty easy (with example):

var array = ['pear', 'apple', 'orange', 'apple', 'orange', 'apple'];            
var res = Enumerable.From(array).GroupBy(function (x) { return x; }).Select(function (x) { return { key: x.Key(), count: x.Count() } }).OrderByDescending(function (x) { return x.count }).Select(function (x) { return x.key}).ToArray();

You could try out lodash. All you need to do is group, sort, then map and you are done.

var arr = ['pear', 'apple', 'orange', 'apple', 'orange', 'apple'];

document.body.innerHTML = _(arr).chain().groupBy()
  .sortBy(function(a) {
    return -a.length;   // <- Note: Remove the negation to sort in ascending order.
  }).map(function(a) {
    return a[0];
  }).value().join(', ');

<script src="https://cdn.rawgit./lodash/lodash/master/dist/lodash.js"></script>

Try this:

var arr = ['pear', 'apple', 'orange', 'apple', 'orange', 'apple'];
var result = [];
var count = 0;

arr.sort();

for (var i = 0; i < arr.length; i++) {
  count++;
  if (arr[i] != arr[i + 1]) {
    result.push({
      "count": count,
      "value": arr[i]
    });
    count = 0;
  }
}

result.sort(function(a, b) {
  if (a.count < b.count) return 1;
  if (a.count > b.count) return -1;
  return 0;
});

console.log(result.map(function(item){return item.value}));

For a legacy JS version i ended up with this.

    function sortByOccurrence(arr_in){
        var arr_out = [];
        var c = {}; // count obj

        for (var i = 0; i < arr_in.length; i++) {
            var p = arr_in[i];
            c[p] = (c[p] || 0) + 1;
        }

        for (var p in c) if ( c.hasOwnProperty(p) ) arr_out.push(p);
        arr_out.sort(function(a, b) { return c[b] - c[a];});
        return arr_out;
    }

本文标签： javascriptSort Array by occurrence of its elementsStack Overflow