Underscore.js sort an array of objects alphanumeri

Question

I have an array of objects and I'm trying to sort them alphanumerically, take the following example:

var objs = {
    'obj1': {'name': 'Object21'},
    'obj2': {'name': 'Object140'},
    'obj3': {'name': 'Object28'},
    'obj4': {'name': 'Object251'}
};

When calling _.sortBy(objs, function(obj) { return obj.name; } the output is:

1. Object140
2. Object21
3. Object251
4. Object28

How can I order this alphanumerically using Underscore? I know I could create a separate array using just the names but is there a better way of doing this using Underscore without creating an additional variable?

Answer 1

You will need to create your own iterator function and then use it, you can't actually do this with the iterator function, but you can get close to it:

var objs = {
    'obj1': {'name': 'Object21'},
    'obj2': {'name': 'Object140'},
    'obj3': {'name': 'Object28'},
    'obj4': {'name': 'AnObject251'}
};

_.sortBy(objs, function(obj) {
    var cc = [], s = obj.name;
    for(var i = 0, c; c = s.charAt(i); i++) 
        c == +c ? cc.push(+c) : cc.push(c.charCodeAt(0));
    return +cc.join('');
});

> Object21
  Object28
  Object140
  AnObject251

"AnObject251" goes on the last place because of its length.

Answer 2

You need the Alphanum sorting algorithm and an elegant implementation in JavaScript:

function alphanum(a, b) {
  function chunkify(t) {
    var tz = [], x = 0, y = -1, n = 0, i, j;

    while (i = (j = t.charAt(x++)).charCodeAt(0)) {
      var m = (i == 46 || (i >=48 && i <= 57));
      if (m !== n) {
        tz[++y] = "";
        n = m;
      }
      tz[y] += j;
    }
    return tz;
  }

  var aa = chunkify(a);
  var bb = chunkify(b);

  for (x = 0; aa[x] && bb[x]; x++) {
    if (aa[x] !== bb[x]) {
      var c = Number(aa[x]), d = Number(bb[x]);
      if (c == aa[x] && d == bb[x]) {
        return c - d;
      } else return (aa[x] > bb[x]) ? 1 : -1;
    }
  }
  return aa.length - bb.length;
}

Answer 3

I've managed to find a solution to this myself using Google :-) here's what I used for those that need this in future and it's actually called "Natural Sorting"

use by calling _.sortByNat(objs, function(obj) { return obj.name; })

/*
* Backbone.js & Underscore.js Natural Sorting
*
* @author Kevin Jantzer <https://gist.github.com/kjantzer/7027717>
* @since 2013-10-17
* 
* NOTE: make sure to include the Natural Sort algorithm by Jim Palmer (https://github.com/overset/javascript-natural-sort)
*/

// add _.sortByNat() method
_.mixin({

    sortByNat: function(obj, value, context) {
        var iterator = _.isFunction(value) ? value : function(obj){ return obj[value]; };
        return _.pluck(_.map(obj, function(value, index, list) {
          return {
            value: value,
            index: index,
            criteria: iterator.call(context, value, index, list)
          };
        }).sort(function(left, right) {
          var a = left.criteria;
          var b = right.criteria;
          return naturalSort(a, b);
        }), 'value');
    }
});

/*
* Natural Sort algorithm for Javascript - Version 0.7 - Released under MIT license
* Author: Jim Palmer (based on chunking idea from Dave Koelle)
* https://github.com/overset/javascript-natural-sort
*/
function naturalSort (a, b) {
    var re = /(^-?[0-9]+(\.?[0-9]*)[df]?e?[0-9]?$|^0x[0-9a-f]+$|[0-9]+)/gi,
        sre = /(^[ ]*|[ ]*$)/g,
        dre = /(^([\w ]+,?[\w ]+)?[\w ]+,?[\w ]+\d+:\d+(:\d+)?[\w ]?|^\d{1,4}[\/\-]\d{1,4}[\/\-]\d{1,4}|^\w+, \w+ \d+, \d{4})/,
        hre = /^0x[0-9a-f]+$/i,
        ore = /^0/,
        i = function(s) { return naturalSort.insensitive && (''+s).toLowerCase() || ''+s },
        // convert all to strings strip whitespace
        x = i(a).replace(sre, '') || '',
        y = i(b).replace(sre, '') || '',
        // chunk/tokenize
        xN = x.replace(re, '\0$1\0').replace(/\0$/,'').replace(/^\0/,'').split('\0'),
        yN = y.replace(re, '\0$1\0').replace(/\0$/,'').replace(/^\0/,'').split('\0'),
        // numeric, hex or date detection
        xD = parseInt(x.match(hre)) || (xN.length != 1 && x.match(dre) && Date.parse(x)),
        yD = parseInt(y.match(hre)) || xD && y.match(dre) && Date.parse(y) || null,
        oFxNcL, oFyNcL;
    // first try and sort Hex codes or Dates
    if (yD)
        if ( xD < yD ) return -1;
        else if ( xD > yD ) return 1;
    // natural sorting through split numeric strings and default strings
    for(var cLoc=0, numS=Math.max(xN.length, yN.length); cLoc < numS; cLoc++) {
        // find floats not starting with '0', string or 0 if not defined (Clint Priest)
        oFxNcL = !(xN[cLoc] || '').match(ore) && parseFloat(xN[cLoc]) || xN[cLoc] || 0;
        oFyNcL = !(yN[cLoc] || '').match(ore) && parseFloat(yN[cLoc]) || yN[cLoc] || 0;
        // handle numeric vs string comparison - number < string - (Kyle Adams)
        if (isNaN(oFxNcL) !== isNaN(oFyNcL)) { return (isNaN(oFxNcL)) ? 1 : -1; }
        // rely on string comparison if different types - i.e. '02' < 2 != '02' < '2'
        else if (typeof oFxNcL !== typeof oFyNcL) {
            oFxNcL += '';
            oFyNcL += '';
        }
        if (oFxNcL < oFyNcL) return -1;
        if (oFxNcL > oFyNcL) return 1;
    }
    return 0;
}

// extend Array to have a natural sort
Array.prototype.sortNat = function(){
    return Array.prototype.sort.call(this, naturalSort)
}