Compare and reduce complex array of objects

Question

I have a ``dataset which is an array of objects for some items in a database that has the details of how long it will take in estimatedDays for a specific item to be shipped:

items : [
    {
    id: '1'
    shippingMethods: [
        {
        id: 'STANDARD',
        estimatedDays: 3,
        },
        {
        id: 'TWODAY',
        estimatedDays: 2,
        },
        {
        id: 'NEXTDAY',
        estimatedDays: 1,
        },
    ]
    },
    {
    id: '2'
    // same shipping data as above but standard shipping will take 4 estimatedDays
    },
    {
    id: '3'
    // same shipping data as above but TWODAY shipping will take 3 estimatedDays
    },
]

I am wondering if there is a reduce function that could compare each shippingMethod.id in each item and return a new array back only where shippingMethod.estimatedDays is greatest compared to all items.

So the end array would be an array of objects with (in this case) 3 shipping methods: STANDARD, TWODAY, and NEXTDAY.

Answer 1

Here you go with the reduce method,

reduce

 var items = [ { id: '1', shippingMethods: [ { id: 'STANDARD', estimatedDays: 3 }, { id: 'TWODAY', estimatedDays: 2 }, { id: 'NEXTDAY', estimatedDays: 1 }, ] }, { id: '2', shippingMethods: [ { id: 'STANDARD', estimatedDays: 4 }, { id: 'TWODAY', estimatedDays: 2 }, { id: 'NEXTDAY', estimatedDays: 1 }, ] }, { id: '3', shippingMethods: [ { id: 'STANDARD', estimatedDays: 3 }, { id: 'TWODAY', estimatedDays: 3 }, { id: 'NEXTDAY', estimatedDays: 1 }, ] }, ]; var outItems = items.reduce(function(accu, curr){ if(curr.shippingMethods) { if(accu.length > 0) { for(var i = 0; i < curr.shippingMethods.length; i++) { var current = curr.shippingMethods[i]; if(accu[i].id === current.id && accu[i].estimatedDays < current.estimatedDays) { accu[i] = current; } } } else { accu = curr.shippingMethods; } } return accu; }, []); console.log(outItems);