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); ... }

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## Answer

For the generic situation of a number of objects with `discount_percent`

s and `quantity`

s, `.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);