Sort javascript Array in a pre-defined order

Question

I have a JavaScript array that I need to sort in a pre-defined order. It seems random, but they do need to be in a specific order.

Here is where I started, but am not sure how to finish:

// Items
var items = ["Apples", "Oranges", "Grapes", "Peaches", "Bananas", "Watermelon"];
var itemsOrdered = {};

// Order how I want them
for (i in items) {
    var item = items[i];
    if (item == 'Apples') {
        itemsOrdered['4'] = item;
    } else if (item == 'Oranges') {
        itemsOrdered['2'] = item;
    } else if (item == 'Grapes') {
        itemsOrdered['1'] = item;
    } else if (item == 'Peaches') {
        itemsOrdered['3'] = item;
    } else if (item == 'Bananas') {
        itemsOrdered['6'] = item;
    } else if (item == 'Watermelon') {
        itemsOrdered['5'] = item;
    }
}

Order should be:

Apples: 4
Oranges: 2
Grapes: 1
Peaches: 3
Bananas: 6
Watermelon: 5

All of these items might not always be in the array. It might only be Apples and Bananas, but they still need the same sort positions.

I have to set this manual sort order after the array is created because our system prints them out in this random order which we then need to sort correctly.

In the end, I need the correctly sorted fruits back in an array.

Ideas?

What do you want at position 0? Why are you using an object instead of an array? — Andrew Whitaker
– Andrew Whitaker, Commented Apr 25, 2013 at 17:40
What is the logic behind such sorting? You can't make an "I-Want-It-Like-That" algorithm. — Artyom Neustroev
– Artyom Neustroev, Commented Apr 25, 2013 at 17:41

Ian · Accepted Answer · 2013-04-25 17:46:01Z

13

Try:

var items = ["Apples", "Bananas", "Watermelons"];
var itemsOrdered = [];
var theOrder = ["Grapes", "Oranges", "Peaches", "Apples", "Watermelons", "Bananas"];

for (var i = 0; i < theOrder.length; i++) {
    if (items.indexOf(theOrder[i]) > -1) {
        itemsOrdered.push(theOrder[i]);
    }
}

console.log(itemsOrdered);

DEMO: http://jsfiddle.net/JPNGS/

The order is defined in theOrder. items contains the available items. itemsOrdered contains the available items, ordered.

answered Apr 25, 2013 at 17:46

Ian

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1 Comment

BaltoStar Over a year ago

Not sure how well this scales ... what if theOrder had 100 or 1000 elements and items only had 10 ?

Reinstate Monica -- notmaynard · Accepted Answer · 2013-04-25 19:50:18Z

13

Put your ordering in an object, like this:

var ordering = {};
ordering["Apples"] = 4;
ordering["Oranges"] = 2;
... // etc.

Then sort your items array using Array.sort(compareFunction(a, b)), passing it a sorting function to check your objects against ordering (left as an exercise). Check out https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/sort to see how compareFunction() is used.

Edit: Here's an implementation:

var ordering = {"Apples":4, "Oranges":2, "Grapes":1, 
                "Peaches":3, "Bananas":6, "Watermelons":5};
var items = ["Apples", "Oranges", "Grapes", 
             "Peaches", "Bananas", "Watermelons"];
items.sort(function(a,b) { return ordering[a] - ordering[b]; })
> ["Grapes", "Oranges", "Peaches", "Apples", "Watermelons", "Bananas"]

edited Apr 25, 2013 at 19:50

answered Apr 25, 2013 at 17:44

Reinstate Monica -- notmaynard

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3 Comments

Artyom Neustroev Over a year ago

You are defining an object, not an array.

Reinstate Monica -- notmaynard Over a year ago

True. I was thinking more of a hash. A plain object works fine, though. Edited.

Johan Maes Over a year ago

You could now use a Map instead of a plain Object for the ordering.

zap · Accepted Answer · 2013-04-25 18:07:38Z

0

First convert your object to an Array:

var sortOrder = [];

for (i in itemsOrdered)
    sortOrder[i-1] = itemsOrdered[i];

Then use .filter() like this:

var result = sortOrder.filter(item) {
    return items.indexOf(item) !== -1;
});

edited Apr 25, 2013 at 18:07

answered Apr 25, 2013 at 17:55

zap

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Comments

Niet the Dark Absol · Accepted Answer · 2013-04-25 17:42:20Z

-2

Your code simplifies to:

var itemsOrdered = {1:"Peaches",2:"Oranges",3:"Grapes",4:"Apples",5:"Watermelon",6:"Bananas"};

In other words, it's completely pointless. Just define them in the order you want them.

answered Apr 25, 2013 at 17:42

Niet the Dark Absol

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1 Comment

Nic Hubbard Over a year ago

I have to set this manual sort order after the array is created because our system prints them out in this random order which we then need to sort correctly.

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