Suppose I have an array of object,
const book = [{'name':'alpha','readingTime':1231},{'name':'alpha','readingTime':1254},
{'name':'beta','readingTime':190},
{'name':'theta','readingTime':909},{'name':'theta','readingTime':10}]
I want to calculate average for each name, such that expected O/P is
**{alpha:1242.5, beta:190, theta:459.5}**
For this I tried as ,
let calculatedValue = book.reduce((acc,curr) => acc+curr.readingTime,0)/book.length
This gives me average for all the object.
I'm unable to form logic corresponding to it.
Any guidance would really be helpful. If anyone needs any further information please let me know.
You could group by name and get the count and total of readingTime and build a new object with the averages.
const
books = [{ name: 'alpha', readingTime: 1231 }, { name: 'alpha', readingTime: 1254 }, { name: 'beta', readingTime: 190 }, { name: 'theta', readingTime: 909 }, { name: 'theta', readingTime: 10 }],
averages = Object.fromEntries(
Object.entries(books.reduce((r, { name, readingTime }) => {
r[name] = r[name] || { count: 0, total: 0 };
r[name].count++;
r[name].total += readingTime;
return r;
}, {}))
.map(([k, { count, total }]) => [k, total / count])
);
console.log(averages);Here is another simple solution for you.
const book = [{'name':'alpha','readingTime':1231},{'name':'alpha','readingTime':1254},
{'name':'beta','readingTime':190},
{'name':'theta','readingTime':909},
{'name':'theta','readingTime':10}]
const result = {};
Object.values(book.reduce((acc, current) => {
acc[current.name] = acc[current.name] || { count: 0, total: 0 };
acc[current.name].total += current.readingTime;
acc[current.name].count += 1;
acc[current.name].name = current.name;
return acc;
}, {})).forEach(({ name, count, total }) => { result[name] = total / count; });
console.log(result)Need more optimization (Fell free to edit ) but it works
const book = [{'name':'alpha','readingTime':1231},{'name':'alpha','readingTime':1254},
{'name':'beta','readingTime':190},
{'name':'theta','readingTime':909},{'name':'theta','readingTime':10}]
function avgReading(arr){
let alpha = { lengtharr : 0 ,readingAll : 0 };
let beta = {...alpha};
let theta = {...alpha};
arr.forEach((item) => {
if(item.name === 'alpha')
alpha.lengtharr++;
alpha.readingAll = alpha.readingAll + item.readingTime;
if(item.name === 'beta')
beta.lengtharr++;
beta.readingAll = beta.readingAll + item.readingTime;
if(item.name === 'theta')
theta.lengtharr++;
theta.readingAll = theta.readingAll + item.readingTime;
});
const obj = {
'alpha' : alpha.readingAll /alpha.lengtharr,
'beta' : beta.readingAll /beta.lengtharr,
'theta' : theta.readingAll /theta.lengtharr
}
return obj;
}
console.log(avgReading(book))