Find matching objects in array by name then add values of matching objects

Question

I have searched stackoverflow for answers but I do not really see anything which solves this. I want to take an objects in an array, match them by their name. Then calculate the total of the matching objects hours value.

If this is the array

var arr = [{name: 'Apple', hours: 6}, {name: 'Nokia', hours: 8}, 
           {name: 'Apple', hours: 4}, {name: 'Nokia', hours: 12},];
//return [{name: 'Apple', totalHrs: '10'}], [{name: 'Nokia', totalHrs: 
         '24'}]

Thank you for any help.

Answer 1

That's not possible, an object literal can't have two identical keys. Instead you could sum the values and take the name as a key

 let arr = [{name: 'Apple',hours: 6}, {name: 'Nokia',hours: 8},{name: 'Apple',hours: 4}, {name: 'Nokia',hours: 12}]; let obj = arr.reduce((a, b) => { a[b.name]= (a[b.name] || 0) + b.hours; return a; }, {}); console.log(obj); 

Answer 2

Use some hashing and for loop

var hash={}; // hash array to contain names and total hours
var arr = [{name: 'Apple', hours: 6}, {name: 'Nokia', hours: 8}, 
           {name: 'Apple', hours: 4}, {name: 'Nokia', hours: 12},];
for(var i=0; i<arr.length; i++)
{
    if(arr[i].name in hash)
        hash[arr[i].name]+=arr[i].hours;
    else
        hash[arr[i].name]=arr[i].hours;
}
console.log(hash);`

Answer 3

You can do this:

function findItemsByProp(array, propName, value) {
        var results = [];
        for (var i = 0; i < array.length; i++) {
            if (array[i][propName] == value)
                results.push(array[i]);
        }
        return results;
    }

This is how to use it:

var matching = findItemsByProp(myArray, 'name', 'someValueOfNameProp');
var total = 0;
for(var i = 0; i < matching.length; i++)
    total += matching[i].hours;

console.log(total);  

of course you can do the sum while iterating over the array, but this is a general method to be used any where else.