Not able to sort array of objects

Question

I have following array:

[
    {
        "BestCoupon": 1,
        "Saving": "100",
        "Successful": 1,
        "couponCode": "CRIC100",
        "description": "Get Rs. 100 Discount on purchase of Rs. 599 & above. Products include Eyeglasses & Sunglasses and more. Choose",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE :Coupon code \"CRIC200\" is not valid.",
        "Successful": 0,
        "couponCode": "CRIC200",
        "description": "Get Rs. 200 Discount on purchase of Rs. 999 & above. Products include Eyeglasses & Sunglasses and more. Choose",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE : Coupon code \"CRIC300\" is not valid.",
        "Successful": 0,
        "couponCode": "CRIC300",
        "description": "Get Rs. 300 Discount on purchase of Rs. 1199 & above. Products include Eyeglasses, Sunglasses & Contact Lenses",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE: Coupon code \"JJPREMIUM\" is not valid.",
        "Successful": 0,
        "couponCode": "JJPREMIUM",
        "description": "Get Rs 600 Discount on John Jacobs Eyeglasses. Products include Eyeglasses. Choose from brand like John",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE: Coupon code \"LENS20130303\" is not valid.",
        "Successful": 0,
        "couponCode": "LENS20130303",
        "description": "Get Rs. 500 Discount on purchase of Rs. 1000. Products include Eyeglasses, Sunglasses & Contact Lenses and",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "179.8",
        "Successful": 1,
        "couponCode": "LKEND20",
        "description": "Get 20% Discount on Eyeglasses. Minimum Purchase Rs. 499. Products include Eyeglasses. Choose from brandslike",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "224.75",
        "Successful": 1,
        "couponCode": "LKEND25",
        "description": "Flat 25% off on purchase of Rs 799 & above",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE : Coupon code \"LKEND30\" is not valid.",
        "Successful": 0,
        "couponCode": "LKEND30",
        "description": "Get 30% Discount on purchase of Rs 1299 & above. Products include Eyeglasses, Sunglasses & Contact Lenses and",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE : Coupon code \"LKEND35\" is not valid.",
        "Successful": 0,
        "couponCode": "LKEND35",
        "description": "Get 35% Discount on purchase of Rs 1499 & above. Products include Eyeglasses, Sunglasses & Contact Lenses and",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "100",
        "Successful": 1,
        "couponCode": "OMGABV600",
        "description": "Get Rs. 100 Discounton order of Rs. 600 & Above. Products include Eyeglasses, Sunglasses & Contact Lenses and",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE : Coupon code \"POWERSUN20\" isnot valid.",
        "Successful": 0,
        "couponCode": "POWERSUN20",
        "description": "Get 20% OFFon Power Sunglasses. Select from a vast collection.",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "179.8",
        "Successful": 1,
        "couponCode": "WEEKEND20",
        "description": "Flat 20% OFF on purchase of Rs 499 & above - NA on Premium Brands & Contact Lenses",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    }
]

I want to sort it in the descending order of "Savings". Am using the following code

couponObj.sort(function (a, b) {
      if (a[0].Saving == b[0].Saving)
         return 0;
      if (a[0].Saving > b[0].Saving)
         return -1;
      if (a[0].Saving < b[0].Saving)
         return 1;
});

Its giving me the following result :

[
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE : Coupon code \"POWERSUN20\" is not valid.",
        "Successful": 0,
        "couponCode": "POWERSUN20",
        "description": "Get 20% OFF on Power Sunglasses. Select from a vast collection.",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE : Coupon code \"LKEND35\" is not valid.",
        "Successful": 0,
        "couponCode": "LKEND35",
        "description": "Get 35% Discount on purchase of Rs 1499 & above. Products include Eyeglasses, Sunglasses & Contact Lenses and",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE : Coupon code \"LKEND30\" is not valid.",
        "Successful": 0,
        "couponCode": "LKEND30",
        "description": "Get 30% Discount on purchase of Rs 1299 & above. Products include Eyeglasses, Sunglasses & Contact Lenses and",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE : Coupon code \"LENS20130303\" is not valid.",
        "Successful": 0,
        "couponCode": "LENS20130303",
        "description": "Get Rs. 500 Discount on purchase of Rs. 1000. Products include Eyeglasses, Sunglasses & Contact Lenses and",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE : Coupon code \"JJPREMIUM\" is not valid.",
        "Successful": 0,
        "couponCode": "JJPREMIUM",
        "description": "Get Rs 600 Discount on John Jacobs Eyeglasses. Products include Eyeglasses. Choose from brand like John",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE : Coupon code \"CRIC300\" is not valid.",
        "Successful": 0,
        "couponCode": "CRIC300",
        "description": "Get Rs. 300 Discount on purchase of Rs. 1199 & above. Products include Eyeglasses, Sunglasses & Contact Lenses",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "NOT APPLICABLE : Coupon code \"CRIC200\" is not valid.",
        "Successful": 0,
        "couponCode": "CRIC200",
        "description": "Get Rs. 200 Discount on purchase of Rs. 999 &above. Products include Eyeglasses & Sunglasses and more. Choose",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "224.75",
        "Successful": 1,
        "couponCode": "LKEND25",
        "description": "Flat 25% off on purchase of Rs 799 & above",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "179.8",
        "Successful": 1,
        "couponCode": "LKEND20",
        "description": "Get 20% Discount on Eyeglasses. Minimum Purchase Rs. 499. Products include Eyeglasses. Choose from brands like",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "179.8",
        "Successful": 1,
        "couponCode": "WEEKEND20",
        "description": "Flat 20%OFF on purchase of Rs 499 & above - NA on Premium Brands & Contact Lenses",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "100",
        "Successful": 1,
        "couponCode": "CRIC100",
        "description": "Get Rs. 100 Discount on purchase of Rs. 599 & above. Products include Eyeglasses & Sunglasses and more. Choose",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    },
    {
        "BestCoupon": 0,
        "Saving": "100",
        "Successful": 1,
        "couponCode": "OMGABV600",
        "description": "Get Rs. 100 Discount on order of Rs. 600 & Above. Products include Eyeglasses, Sunglasses & Contact Lenses and",
        "domain": "www.lenskart.com",
        "url": "http://www.lenskart.com/checkout/cart/"
    }
]

Basically it's sorting on top the array item where saving is a string. I want them at bottom.

I've edited your question to remove references to JSON since it doesn't seem to have any relation with it. Feel free to correct if I'm wrong. — Álvaro González
– Álvaro González, Commented Sep 3, 2013 at 12:18
A small suggestion: have an additional key called SavingText and move that 'Not applicable' text to there and set Saving to 0. — Andy
– Andy, Commented Sep 3, 2013 at 12:19
If you're confused about what they were talking about, JSON is a way of putting data in a string for transfer, while an object is how the actual data structure is used within JavaScript — Qantas 94 Heavy
– Qantas 94 Heavy, Commented Sep 3, 2013 at 12:29

Paul S. · Accepted Answer · 2013-09-03 13:26:58Z

3

Looks like you're trying to access a property 0 of your object which doesn't appear to exist; and at the same time as correcting that, make it easier to see what's going on.

couponObj.sort(function (a, b) {
    a = +a.Saving, b = +b.Saving; // cast Number
    // special cases
    if (a !== a || b !== b)           // If there is a NaN
        return (a !== a) - (b !== b); // move it to the end
    // classic descending sort
    return b - a;
});

edited Sep 3, 2013 at 13:26

answered Sep 3, 2013 at 12:17

Paul S.

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7 Comments

xanatos Over a year ago

+1 Why not the classical return b - a? Is there something different in JS?

xanatos Over a year ago

I asked because one can never know with weak-typed languages like JS... perhaps there was something hidden (like your use of ===, but that at least I know)

xanatos Over a year ago

considering he has various NaN values (the "text" values), perhaps it would be better to handle them as a special case :-)

Paul S. Over a year ago

@xanatos we know it's fine in this example because I already did a cast. You may have to consider if it will be okay if there was no cast and you expect different types

Paul S. Over a year ago

The NaN won't get moved, true. Let me fix this.

|

xanatos · Accepted Answer · 2013-09-03 12:39:51Z

1

As other have suggested, but with a caveat: you have various Saving that are text instead of descriptions...

couponObj.sort(function (a, b) {
    a = parseFloat(a.Saving); // cast to number
    b = parseFloat(b.Saving); // cast to number

    if (isNaN(a)) return isNaN(b) ? 0 : 1;
    if (isNaN(b)) return -1;

    return b - a; // descending order
});

When you try casting a non-number to a number with +, the returned number is NaN (a special value that doesn't sort very well). For this reason the various if (isNaN())

Note that in initial versions I had used +a.Saving to cast the string to a number, but I've changed it to parseFloat. There is a subtle difference with null: +null === 0, while parseFloat(null) === NaN (that then I can handle).

edited Sep 3, 2013 at 12:39

answered Sep 3, 2013 at 12:28

xanatos

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7 Comments

Oleg Over a year ago

And let's hope a and b are not null ;)

xanatos Over a year ago

@Oleg +null is 0... mmmmh

Oleg Over a year ago

+null.Saving -> "TypeError: Cannot read property 'Saving' of null" because the property will be read before attempting to "cast" to number.

xanatos Over a year ago

@Oleg Ah... No I was thinking of a.Saving that could be null or undefined

Paul S. Over a year ago

Looks nice and neat. The example JSON did not have any null entries, so I don't think we need to worry unless it get's said by OP

|

Oleg · Accepted Answer · 2013-09-03 12:49:05Z

0

When the comparator function is supplied to Array.prototype.sort, it is given arguments a and b which are elements of the original array, not the array itself.

So, in this particular case, you need to drop [0]. For example, instead of:

if (a[0].Saving == b[0].Saving) { ...

try:

if (a.Saving === b.Saving) { ...
           // ^-- also, it's best to use strict comparison

edited Sep 3, 2013 at 12:49

answered Sep 3, 2013 at 12:17

Oleg

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Comments

Krešimir Prcela · Accepted Answer · 2013-09-03 12:50:33Z

0

Use the parseFloat method for the string conversion to floats:

couponObj.sort(function (a, b) {
  if(a && b) {
    var af = parseFloat(a.Saving);
    var bf = parseFloat(b.Saving);
    if(isNan(af)) return 1;
    if(isNan(bf)) return -1;
    return bf-af;
  }
  return 0; // ignore null entries
}

edited Sep 3, 2013 at 12:50

answered Sep 3, 2013 at 12:34

Krešimir Prcela

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