I have the following array
[{price: 65, date: 11-02-2020}, {price: 69, date: 11-02-2020}, {price: 34, date: 11-02-2020}]
How could I make an array of prices and an array dates. Without having to use a for or foreach loop?
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1What is wrong with using a loop?Scott Hunter– Scott Hunter2020-02-11 13:13:21 +00:00Commented Feb 11, 2020 at 13:13
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I meant for / foreach loop. Could this be done with array.map() ? Or some function that doesn't obfuscate the code?OneDayFly– OneDayFly2020-02-11 13:17:07 +00:00Commented Feb 11, 2020 at 13:17
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In what way does a for loop obfuscate the code?Scott Hunter– Scott Hunter2020-02-11 13:34:11 +00:00Commented Feb 11, 2020 at 13:34
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1 Answer
You can use map() to build an array with specific members :
const datas = [{price: 65, date: '11-02-2020'}, {price: 69, date: '11-02-2020'}, {price: 34, date: '11-02-2020'}];
const prices = datas.map(elem => elem.price);
const dates = datas.map(elem => elem.date);
console.log(prices);
console.log(dates);However, this does 2 loops under the hood. Using a good old loop can divide the time complexity by 2 :
const datas = [{price: 65, date: '11-02-2020'}, {price: 69, date: '11-02-2020'}, {price: 34, date: '11-02-2020'}];
const prices = [];
const dates = [];
for (let i = 0, len = datas.length; i < len; i++)
{
prices.push(datas[i].price);
dates.push(datas[i].date);
}
console.log(prices);
console.log(dates);5 Comments
Scott Hunter
I'd be surprised if the good old loop halved the execution time; it wouldn't surprise me if it actually ran slower.
Cid
@ScottHunter could be, indeed, we might need some benchmarks
Scott Hunter
So "can divide the time complexity by 2" was a bit premature?
Cid
Well, that's a supposition, hence the "can" instead of "will"
Scott Hunter
Except it can't since you still do the same number of
pushes. So, at best, you've eliminated 1/2 of the work done by (at best) half of the code.