Get matched range item from array of objects javascript

Question

I have one array which is named as tiers and one quantity variable. Now I am trying to get the matched range value from my tier array. Based on the matched result I want to calculate the discount. I tried to with find method but it gives me an unexpected ouput.

Actual output {id: 1, discount_percent:0, quantity:6, title:"Tier 1"}

Expeceted Output {id: 3, discount_percent:10, quantity:10, title:"Tier 3"}

let tiers = [
   {id: 1, discount_percent:0, quantity:6, title:"Tier 1"},
   {id: 2, discount_percent:5, quantity:8, title:"Tier 2"},
   {id: 3, discount_percent:10, quantity:10, title:"Tier 3"},
   {id: 4, discount_percent:12, quantity:12, title:"Tier 4"},
   {id: 5, discount_percent:14, quantity:14, title:"Tier 5"},
   {id: 6, discount_percent:20, quantity:16, title:"Tier 6"},
   {id: 7, discount_percent:40, quantity:18, title:"Tier 7"},
   {id: 8, discount_percent:50, quantity:50, title:"Tier 8"},
]

function calculateDiscount(){
   const ordersQuanity = 10;
   const tier = tiers.find((_tier) => _tier.quantity <= ordersQuanity);
   ...
}

_tier.quantity <= ordersQuanity this should be _tier.quantity >= ordersQuanity You need to find the first object where quantity is greater than or equal to given threshold — Rajesh Dixit
– Rajesh Dixit, Commented Jan 6, 2023 at 6:03

CertainPerformance · Accepted Answer · 2023-01-07 20:56:39Z

1

For the generic situation of a number of objects with discount_percents and quantitys, .find isn't the right approach because it'll stop as soon as it finds a match. Consider .reduce instead - if an element being iterated over passes the test and it has a greater discount_percent than the current element in the accumulator (if there's anything in the accumulator to begin with), return it instead.

let tiers = [
   {id: 1, discount_percent:0, quantity:6, title:"Tier 1"},
   {id: 2, discount_percent:5, quantity:8, title:"Tier 2"},
   {id: 3, discount_percent:10, quantity:10, title:"Tier 3"},
   {id: 4, discount_percent:12, quantity:12, title:"Tier 4"},
]
function calculateDiscount(){
   const ordersQuanity = 10;
   const bestTier = tiers.reduce((a, tier) => (
     tier.quantity <= ordersQuanity && (!a || tier.discount_percent > a.discount_percent)
       ? tier
       : a
   ), null) || tiers[0]; // alternate with the first element of the array
   // if you want to default to that tier even if the quantity isn't sufficient
   console.log(bestTier);
}
calculateDiscount();

If you happen to be able to assume that every increased discount_percent comes with a larger quantity, and the array is sorted, you can use .find if you reverse the array first (so that the items with the greatest discount_percent are iterated over first).

let tiers = [
   {id: 1, discount_percent:0, quantity:6, title:"Tier 1"},
   {id: 2, discount_percent:5, quantity:8, title:"Tier 2"},
   {id: 3, discount_percent:10, quantity:10, title:"Tier 3"},
   {id: 4, discount_percent:12, quantity:12, title:"Tier 4"},
];
const tiersReversed = [...tiers].reverse();
function calculateDiscount(){
   const ordersQuanity = 10;
   const tier = tiersReversed
     .find((_tier) => _tier.quantity <= ordersQuanity)
      || tiers[0]; // alternate with the first element of the array
   // if you want to default to that tier even if the quantity isn't sufficient
   console.log(tier);
}
calculateDiscount();

The snippet works just as well for the dataset in the edited question.

let tiers = [
   {id: 1, discount_percent:0, quantity:6, title:"Tier 1"},
   {id: 2, discount_percent:5, quantity:8, title:"Tier 2"},
   {id: 3, discount_percent:10, quantity:10, title:"Tier 3"},
   {id: 4, discount_percent:12, quantity:12, title:"Tier 4"},
   {id: 5, discount_percent:14, quantity:14, title:"Tier 5"},
   {id: 6, discount_percent:20, quantity:16, title:"Tier 6"},
   {id: 7, discount_percent:40, quantity:18, title:"Tier 7"},
   {id: 8, discount_percent:50, quantity:50, title:"Tier 8"},
]
function calculateDiscount(ordersQuanity){
   const bestTier = tiers.reduce((a, tier) => (
     tier.quantity <= ordersQuanity && (!a || tier.discount_percent > a.discount_percent)
       ? tier
       : a
   ), null) || tiers[0]; // alternate with the first element of the array
   // if you want to default to that tier even if the quantity isn't sufficient
   console.log(bestTier);
}
calculateDiscount(10);
calculateDiscount(20);

edited Jan 7, 2023 at 20:56

answered Jan 6, 2023 at 6:05

CertainPerformance

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6 Comments

RAHUL KUNDU Over a year ago

both of the approaches are working, but if the quantity is less then any tier quantity then it returns null or undefined. Please check with const ordersQuanity = 5. In that case what should I do? please suggest?

CertainPerformance Over a year ago

Yes, that's what your data would seem to indicate the expected output would be. If the threshold for the lowest tier is quantity: 6, then quantity: 5 will not pass any thresholds.

RAHUL KUNDU Over a year ago

In that case, if does not match any tier I want the first tier to be returned, is there any way I can return the first tier within the reduce or find method?

CertainPerformance Over a year ago

I'd move the condition outside. eg .reduce(...) || tiers[0]

RAHUL KUNDU Over a year ago

I am reopening the issue because, if the quantity is 20 then the solutions are not working.

|

lunatic · Accepted Answer · 2023-01-09 06:13:11Z

0

`function discountPercent(item){ return item.discount_percent == 10 }

console.log(tiers.find(discountPercent))

answered Jan 9, 2023 at 6:13

lunatic

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