Counting arrays by distinct value

I have an array of arrays. Each contains a list of information along with an id as below:

let array = [
['value1', 'value2', 'value3', 'value4', 'value5', 'id_1'], 
['value1', 'value2', 'value3', 'value4', 'value5', 'id_1'],
['value7', 'value8', 'value9', 'value10', 'value11', 'id_3'],
['value20', 'value21', 'value22', 'value23', 'value24', 'id_4'],
['value20', 'value21', 'value22', 'value23', 'value24', 'id_5'],
];

I want to count the distinct instances of each array. When comparing two arrays, if all indexes are the same, including the id, then this means the array is a duplicate and only 1 instance should be counted.

If all indexes are the same, but the id is different, then this means that this is a distinct instance of the array and should be added to the count.

The information needs to be displayed in an object as below. I am struggling to visualise how to accomplish this, my current approach is to remove the ids from arrays, add these to the object and then figure out a way to count the unique instances – but unsure if this is the most effective way to accomplish this.

let obj = [
{
  array=['value1', 'value2', 'value3', 'value4', 'value5'],
  count=1
},
{
  array=['value7', 'value8', 'value9', 'value10', 'value11'],
  count=1
},
{
  array=['value20', 'value21', 'value22', 'value23', 'value24'],
  count=2
}
];

>Solution :

You can use something like this.

I iterated over the array, joined all array values except the last one (id) and then used the joined string as a hash value for my map object and then checked if the id is is different then update the count else dont change

const arr = [['value1', 'value2', 'value3', 'value4', 'value5', 'id_1'], ['value1', 'value2', 'value3', 'value4', 'value5', 'id_1'], ['value7', 'value8', 'value9', 'value10', 'value11', 'id_3'], ['value20', 'value21', 'value22', 'value23', 'value24', 'id_4'], ['value20', 'value21', 'value22', 'value23', 'value24', 'id_5'], ];
    
const map = {};
    
arr.forEach(x=>{
    const key = x.slice(0, -1).join('-');
    const id = x.at(-1);
    if (!map[key]) {
        map[key] = {
            count: 1,
            id,
        };
    } else {
        if (id !== map[key].id)
            map[key].count++;
    }
});
    
console.log(map);
    
const obj = Object.entries(map).map(([k, v])=>({array:k.split('-'), count: v.count}))
        
console.log(obj);