Sorting a string of numbers received via query string

Question

For my application I am passing in a string of numbers via query string and would like to find the median of all the numbers. This task is pretty simple when working with actual numbers, but considering that I am trying to find the median of a string of numbers, I must convert the string into an array, sort it, convert the nums to integers etc. How could I achieve this result? Here is how I tried to achieve this:

 let nums = req.query
 let numArr = undefined

    for(let x in nums) {
        strX = nums[x].replace(/,/g, '').split('').sort();
        numArr = strX.map(x => parseInt(x))
    }

This method does not work for examples such as '5,7,9,1,12' because it sorts the array like this [1,1,2,5,7,9]

1. Is req.query a string of numbers (e.g. 5,7,9,1,12)? 2. You are overwriting numArr for every number, which doesn't seem like what you want to do. Are you intending for numArr to be the string of numbers converted into integers? — Anson Miu
– Anson Miu, Commented Apr 6, 2021 at 20:24
When you replace the commas, the result is '579112'. When you split this by '', the result is '5,7,9,1,1,2'. — Isaac
– Isaac, Commented Apr 6, 2021 at 20:25

Clem · Accepted Answer · 2021-04-06 20:27:34Z

3

Default behavior of Array.sort is to compare item as UTF16 strings. But you can override that behavior by using your compare function.

'5,7,9,1,12'.split(',').map(n => parseInt(n, 10)).sort((a,b) => a - b)

answered Apr 6, 2021 at 20:27

Clem

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3 Comments

GirkovArpa Over a year ago

Why n => parseInt(n, 10) instead of Number or even just n=>+n?

jarmod Over a year ago

OK as long as the array doesn't contain Infinity or NaN.

Clem Over a year ago

Cause +n is a trick. parseInt is explicit.

Nina Scholz · Accepted Answer · 2021-04-06 20:31:25Z

1

You could take a the string as part of a JSON string and get an array of numbers, sort it and get the median value, depending of the length of the array.

const
    string = '5,7,9,1,12',
    array = JSON
        .parse(`[${string}]`)
        .sort((a, b) => a - b),
    median = array.length % 2
        ? array[array.length >> 1]
        : (array[(array.length >> 1) - 1] + array[array.length >> 1]) / 2;

console.log(...array);
console.log(median);

edited Apr 6, 2021 at 20:31

answered Apr 6, 2021 at 20:26

Nina Scholz

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4 Comments

GirkovArpa Over a year ago

What if string contains duplicate numbers?

Nina Scholz Over a year ago

@GirkovArpa, it does not matter for getting a media, if a number occures more then one time.

Anson Miu Over a year ago

The custom sorting comparator function is redundant as the default behaviour for sort() on numbers is to sort them in ascending order.

Nina Scholz Over a year ago

@AnsonMiu, no, because the Array#sort without callback sorts strings, so you get 11 < 2 and this is not wanted.

Norse · Accepted Answer · 2021-04-06 20:53:19Z

0

You should do this:

 let nums = req.query
 let numArr = undefined

 for(let x in nums) {
     strX = nums[x].split(',').map(x => parseInt(x)).sort((x,y) => x - y);
 }

However I think the loop is redundant, though I haven't tested it. That is, you can do

 let nums = req.query
 let numArr = nums.split(",").map(x => parseInt(x)).sort((x,y) => x - y);

edited Apr 6, 2021 at 20:53

answered Apr 6, 2021 at 20:22

Norse

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2 Comments

Anson Miu Over a year ago

Should do .sort() after .map(), because ["1", "2", "12"] will be sorted as ["1", "12", "2"] in their string representations, as supposed to [1, 2, 12] in their numerical forms.

Anson Miu Over a year ago

+as per the comment from @Nina Scholz , the sort() function will sort by string lexicographical order, so a custom comparator .sort((x, y) => x - y) is needed

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