Comparing 2 arrays in java script

Question

How to compare one sorted descending array and one unsorted array in javascript and unsorted array elements location in the sorted one.

so if the number of elements is 7 in sorted array

[100,90,80,70,60,50,40]

and number of elements in unsorted array is 4 unsorted array is

[200,10,55,65]

then the output will be

How did you get 1 8 6 5 for your output..? I'm not sure what you mean — chevybow
– chevybow, Commented Aug 15, 2018 at 19:07
Is that output supposed to be something like the index at which you'd need to insert the new elements? It's not, exactly, because JS is zero-based, but it looks as though it's something like that. — Scott Sauyet
– Scott Sauyet, Commented Aug 15, 2018 at 19:10
when 200 is encountered in array it is sent at index 1 which makes the array 200 100 90 80 70 60 50 40.for 10 it goes to end of array makes it at position 8.for 55 it goes to position 6 and for 65 it goes to position 5.Kindly do not make changes to the original array. I just want to know the index of the other array elements in previous one — vinayak shahdeo
– vinayak shahdeo, Commented Aug 15, 2018 at 19:59

Mark · Accepted Answer · 2018-08-15 19:18:06Z

2

It looks like you want to find the index (one-based) of where each element would fit into the sorted array. You should be able to do this with map() and findIndex():

let arr = [100,90,80,70,60,50,40]
let a2 = [200,10,55,65]

let indexes = a2.map(n => {
    // find the first place in arr where it's less than n
    let ind = arr.findIndex(i => i < n)  

    // if n wasn't found, it is smaller than all items: return length + 1
    return (ind === -1) ? arr.length + 1 : ind  + 1
})
console.log(indexes)

answered Aug 15, 2018 at 19:18

Mark

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2 Comments

vinayak shahdeo Over a year ago

can you please elaborate the return part??

Mark Over a year ago

Sure @vinayak_shahdeo thats a ternary operator. It says if ind === -1 just return the length of the array +1 otherwise return the ind +1. ind will be -1 if the number you're looking at is smaller than all items int the array (such as 10 in this example). In that case findIndex() doesn't find the index because there are no smaller elements. So it returns -1. The ternary operator lets us test for that special case and return the right value.

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