Filtering and sorting a JSON array

Question

records = [
        {
            name: "Alpha",
            set: 5,
            weight: 185
        },      
        {
            name: "Alpha",
            set: 5,
            weight: 350
        },        
        {
            name: "Bravo",
            set: 5,
            weight: 185
        },        
        {
            name: "Charlie",
            set: 5,
            weight: 185
        },         
        {
            name: "Delta",
            set: 5,
            weight: 185
        }
]

I have a JSON array of multiple records and I need to filter these records by name and weight. So for example, since there are two "Alpha" records, I need to only pull in the one with the highest weight (which would be the second record). I have no idea how to filter and rebuild this array with only the desired results.

I need to keep the original array intact as I'll be displaying ALL in a table, but I need to build a secondary array with only the objects with the greatest value, by name.

Answer 1

You can use lodash 4+ for this.

var sortedArray = _.orderBy(records, ['weight'], ['desc']);

This will sort the array by weight. Then , _.uniqBy(sortedArray,'name')

This will return the final array.

var records = [
        {
            name: "Alpha",
            set: 5,
            weight: 185
        },      
        {
            name: "Alpha",
            set: 5,
            weight: 350
        },        
        {
            name: "Bravo",
            set: 5,
            weight: 185
        },        
        {
            name: "Charlie",
            set: 5,
            weight: 185
        },         
        {
            name: "Delta",
            set: 5,
            weight: 185
        }
]

var sortedArray = _.orderBy(records, ['weight'], ['desc'])

_.uniqBy(sortedArray,'name')

Answer 2

I recommend a functional programming approach:

var newRecords = records
    .filter(function(record) { 
        return records.find(function(innerRecord) {
            return innerRecord.name === record.name && innerRecord.weight > record.weight; }) === undefined;
     });

In this example, you return only records where you cannot find a record sharing the same name but with a larger weight. Also, your newly re-built array is stored in newRecords , leaving your original array intact.

Answer 3

This first sorts the items in name order and weight order and then filter out all but the first of each item.

 var records = [{ name: "Alpha", set: 5, weight: 185 }, { name: "Alpha", set: 5, weight: 350 }, { name: "Bravo", set: 5, weight: 185 }, { name: "Charlie", set: 5, weight: 185 }, { name: "Charlie", set: 5, weight: 200 }, { name: "Delta", set: 5, weight: 185 } ] console.log( records.sort((a, b) => { if (a.name === b.name) { return a.weight >= b.weight ? -1 : 1 } return a.name > b.name ? 1 : -1 }) .filter((rec, i, arr) => { if (i === 0) return true return rec.name !== arr[i - 1].name }) ) 

Answer 4

I recommend you start using lodash and dont spend time to create your own functions. For example, to sort your array by name you should write the following code:

    var records = [
        {
            name: "Alpha",
            set: 5,
            weight: 185
        },      
        {
            name: "Alpha",
            set: 5,
            weight: 350
        },        
        {
            name: "Bravo",
            set: 5,
            weight: 185
        },        
        {
            name: "Charlie",
            set: 5,
            weight: 185
        },         
        {
            name: "Delta",
            set: 5,
            weight: 185
        }
];
var sorted = _.sortBy(records, ['name']);

And second case, to filter by name and weight

var filtered = _.filter(records, [ 'name': 'Alpha', 'weight': 350 ]);