Sort javascript array of objects by child properties (which may be missing)

Question

I have a large-ish dataset (from 400 - 4,000 objects stored in an array), and I'm trying to filter them by a user-selected field.

Right now I'm using this function, found on another SO question:

var sort = function (prop, arr) {
    prop = prop.split('.');
    var len = prop.length;

    arr.sort(function (a, b) {
        var i = 0;
        while( i < len ) {
            a = a[prop[i]];
            b = b[prop[i]];
            i++;
        }
        if (a < b) {
            return -1;
        } else if (a > b) {
            return 1;
        } else {
            return 0;
        }
    });
    return arr;
};

Sample data - I want to sort the objects by the friends count:

var data = [
    {
        name: 'Jim',
        friends: {
            count: 20,
            url: 'http://foo.com'
        }
    },{
        name: 'Lucy',
    },{
        name: 'Phil',
        friends: {
            count: 450,
            url: 'http://moo.com'
        }
    }
];

Notice how "Lucy" doesn't have a friends object - so when I run sort('friends.count', data);, the script breaks.

Ideally I'd like the objects which don't have the property that I'm sorting by to be put at the end of the array. Any ideas on how this can be achieved?

The sample array is already sorted, right?

thefourtheye
– thefourtheye

2015-03-15 08:12:34 +00:00
Commented Mar 15, 2015 at 8:12 — thefourtheye
– thefourtheye, Commented Mar 15, 2015 at 8:12

georg · Accepted Answer · 2015-03-15 10:13:06Z

3

For example,

var data = [
    {
        name: 'Jim',
        friends: {
            count: 20,
            url: 'http://foo.com'
        }
    },{
        name: 'Lucy',
    },{
        name: 'Phil',
        friends: {
            count: 450,
            url: 'http://moo.com'
        }
    }
];

safeGet = function(obj, prop, defaultValue) {
  try {
    return obj[prop]
  } catch(e) {
    return defaultValue
  }
}


data.sort(function(x, y) {
  return (
    safeGet(x.friends, 'count', Infinity) - 
    safeGet(y.friends, 'count', Infinity));
});

document.write("<pre>" + JSON.stringify(data,0,3));

If the whole property chain (friends.count) is dynamic, change safeGet so that it iterates the list of props:

var data = [
    {
        name: 'Jim',
        friends: {
            count: 20,
            url: 'http://foo.com'
        }
    },{
        name: 'Lucy',
    },{
        name: 'Phil',
        friends: {
            count: 450,
            url: 'http://moo.com'
        }
    }
];

safeGet = function(obj, props, defaultValue) {
  try {
    return props.split('.').reduce(function(obj, p) {
      return obj[p];
    }, obj);
  } catch(e) {
    return defaultValue
  }
}


data.sort(function(x, y) {
  return (
    safeGet(x, 'friends.count', Infinity) - 
    safeGet(y, 'friends.count', Infinity));
});

document.write("<pre>" + JSON.stringify(data,0,3));

If you want people with no friends to go first, not last, change Infinity to -Infinity.

edited Mar 15, 2015 at 10:13

answered Mar 15, 2015 at 8:23

georg

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2 Comments

georg Over a year ago

@zaynetro: it's cleaner this way.

zaynetro Over a year ago

if(obj && obj.hasOwnProperty(prop)) can work. Try-catch causes performance issues

zaynetro · Accepted Answer · 2015-03-15 08:29:38Z

1

Your function can be modified to check for the existence of a property:

var sort = function (prop, arr) {
    prop = prop.split('.');
    var len = prop.length;

    arr.sort(function (a, b) {
        var i = 0;
        var key;

        while( i < len ) {
            key = prop[i];

            if(!a.hasOwnProperty(key)) return 1;
            if(!b.hasOwnProperty(key)) return -1;

            a = a[key];
            b = b[key];
            i++;
        }
        if (a < b) {
            return -1;
        } else if (a > b) {
            return 1;
        } else {
            return 0;
        }
    });
    return arr;
};

This way it will be working. I made a jsbin for the example.

@georg's answer wouldn't work with property selected dynamically.

answered Mar 15, 2015 at 8:29

zaynetro

2,30823 silver badges29 bronze badges

2 Comments

JVG Over a year ago

This one worked, except when I tried to sort descending it put "Lucy" first. I changed if(!a.hasOwnProperty(key)) to return -1 and it worked - I'm assuming this is correct, as I want any object which doesn't have the property to go to the end of the array.

zaynetro Over a year ago

True, you mentioned that elements without the property should be put in the end

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