获取分组数组的值索引

Question

I have an array of Ids

 [1,1,1,2,2,2,3,3,...]

And another array of values

[0,1,0,0,0,1,1,0,...]

I need to know what the zero-based index of the group of Ids is, where the corresponding value is 1 in JavaScript.

So for this array, we might get
[1,2,0,...] because that is the index of the 1 in the Values array if you were to group the Id array by their unique values.

There should only be a single 1 per group of Ids. There is a possibility that the group of Ids may be out of sequential order

(ie [1,1,2,1,2,2,3,3,...] ).

But I would still want whatever the index is when the Id array is grouped.

I tried a while loop but kept getting duplicate values. Then I tried to filter my array. How can I accomplish this in JS?

Examples:

array 1 (IDs) : [1,1,1,2,2,2,3,3,3,3] .   
array 2 (values) : [0,1,0,0,1,0,0,0,0,1] .  
result array: [1,1,3] .  

array 3 (IDs) : [1,2,1,3,1,1,2,2,3] .  
array 4 ( values) : [0,0,1,0,0,0,1,0,1] .  
result array : [1,1,1] . 

Answer 1

You could take an index counter for the same group and get the value if a value with one is found.

Example 3:

 [1, 2, 1, 3, 1, 1, 2, 2, 3] ids [0, 0, 1, 0, 0, 0, 1, 0, 1] values 0 0 1 0 2 3 1 2 1 indices by group ^ ^ ^ result 

 function getIndices(ids, values) { var map = new Map; return ids.reduce((r, v, i) => { if (values[i] === 1) r.push(map.get(v) || 0); map.set(v, (map.get(v) || 0) + 1); return r; }, []); } // [1, 2, 0] console.log(...getIndices([1, 1, 1, 2, 2, 2, 3, 3], [0, 1, 0, 0, 0, 1, 1, 0])); // [1, 1, 3] console.log(...getIndices([1, 1, 1, 2, 2, 2, 3, 3, 3, 3], [0, 1, 0, 0, 1, 0, 0, 0, 0, 1])); // [1, 1, 1] console.log(...getIndices([1, 2, 1, 3, 1, 1, 2, 2, 3], [0, 0, 1, 0, 0, 0, 1, 0, 1]));

Instead of a Map , you could take an object as hash table for indexing the values.

 function getIndices(ids, values) { var hash = Object.create(null); return ids.reduce((r, v, i) => { hash[v] = hash[v] || 0; if (values[i] === 1) r.push(hash[v]); hash[v]++; return r; }, []); } // [1, 2, 0] console.log(...getIndices([1, 1, 1, 2, 2, 2, 3, 3], [0, 1, 0, 0, 0, 1, 1, 0])); // [1, 1, 3] console.log(...getIndices([1, 1, 1, 2, 2, 2, 3, 3, 3, 3], [0, 1, 0, 0, 1, 0, 0, 0, 0, 1])); // [1, 1, 1] console.log(...getIndices([1, 2, 1, 3, 1, 1, 2, 2, 3], [0, 0, 1, 0, 0, 0, 1, 0, 1]));