Sorting an array based on first digit of property

Question

I'm trying to sort an array based on the first digit encountered in the title.

My attempt was replacing the non-numeric characters with '' (title.replace(/\D/g, ''). It gives me back the digits but I'm not sure how to sort the array from this point.

So, test0 first followed by test1, test2 and test3.

model = [
  {
    "title": "test3"
  },
  {
    "title": "test1"
  },
  {
    "title": "test2"
  },
  {
    "title": "test0"
  }
];

Closely related: [Sorting an array of JavaScript objects](http://stackoverflow.com/questions/979256/sorting-an-array-of-javascript-objects) and [Sorting objects in an array by a field value in JavaScript](http://stackoverflow.com/questions/1129216/sorting-objects-in-an-array-by-a-field-value-in-javascript). You already know how to transform the field to your liking, so simply perform that transformation on the field in your comparison function. — apsillers, Dec 29 '14 at 21:32

Wondercricket · Accepted Answer · 2014-12-29T22:03:56.317

5

You can your use regex within Javascript's sort function, like the following.

var model = [
    {
        "title": "test3"
    },
    {
        "title": "test1"
    },
    {
        "title": "test2"
    },
    {
        "title": "test0"
    }
];

Update:

As Danilo Valente stated in comments, if your integer begins with a 0, you need to extract the first 0 from the string. Since 02 => 0

model.sort(function (a, b) {
    //Strips out alpha characters
    a = a.title.replace(/\D/g, '');
    b = b.title.replace(/\D/g, '');

    //sets value of a/b to the first zero, if value beings with zero.
    //otherwise, use the whole integer.
    a = a[0] == '0' ? +a[0] : +a;
    b = b[0] == '0' ? +b[0] : +b;

    return a - b;
});

edited Dec 29 '14 at 22:03

answered Dec 29 '14 at 21:33

Wondercricket

7,651
2
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2

He wants to sort based on the first digit, but in your case if we had `"title02"` it would appear after `"test1"`. – Danilo Valente Dec 29 '14 at 21:36
@DaniloValente Ah, yes. Thanks for pointing that out! I updated my code to cast `a` and `b` as integers. – Wondercricket Dec 29 '14 at 21:39
First you have to extract only the first digit so `02 => 0` and then compare both: `0 < 1`. – Danilo Valente Dec 29 '14 at 21:43
@DaniloValente I tested the updated code before I posted it, and it sorted properly for me. – Wondercricket Dec 29 '14 at 21:43
I did too, and it still doesn't work. Replace `"test0"` with `"test02"` and you'll see. The result should be `["test02", "test1", "test2", "test3"]`, but instead it returns `["test1", "test2", "test02", "test3"]`. – Danilo Valente Dec 29 '14 at 21:45
@DaniloValente oh, I see what you mean now! That was a derp on my end, it "looked" correct when I ran it :) I'll update my code appropriately. – Wondercricket Dec 29 '14 at 21:50

brbcoding · Answer 2 · 2014-12-29T22:39:31.260

4

var model = [{
  "title": "test3"
}, {
  "title": "test1"
}, {
  "title": "test2"
}, {
  "title": "test02"
}, {
  "title": "test0"
}];

// pass a custom sort fn to `.sort()`
var sortedModel = model.sort(function(a, b) {
  // just get the first digit
  return a.title.match(/\d/) - b.title.match(/\d/);
});

console.log(sortedModel);

// [ { title: 'test02' },
//   { title: 'test0' },
//   { title: 'test1' },
//   { title: 'test2' },
//   { title: 'test3' } ]

edited Dec 29 '14 at 22:39

answered Dec 29 '14 at 21:34

brbcoding

13,378
2
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51

He wants to sort based on the first digit, but in your case if we had `"title02"` it would appear after `"test1"`. – Danilo Valente Dec 29 '14 at 21:37

score 0 · Answer 3 · answered Dec 29 '14 at 21:34

Since you want to sort based only on first digit, you can call .sort with a custom function and then use a simple regex to find the first digit:

model.sort(function (a, b) {
    var da = a.title.match(/\d/);
    var db = b.title.match(/\d/);
    return parseInt(da) - parseInt(db);
});

Sorting an array based on first digit of property

3 Answers3

Update: