Convert an array of arrays as items to object with objects as items

Question

I have an array like this:

var arr = [
    ['a1','b1','c1','d1'],
    ['a1','e1','i1','j1'],
    ['a1','f1','k1','l1'],
    ['a1','g1','m1','n1'],
    ['a1','h1','o1','p1'],
    ['a2','b2','c2','d2'],
    ['a2','e2','i2','j2'],
    ['a2','f2','k2','l2'],
    ['a2','g2','m2','n2'],
    ['a2','h2','o2','p2']
];

and I want to convert it to an object like this:

var converted_arr = {
    'a1':{
        'b1':['c1','d1'],
        'e1':['i1','j1'],
        'f1':['k1','l1'],
        'g1':['m1','n1'],
        'h1':['o1','p1'],
    },
    'a2':{
        'b2':['c2','d2'],
        'e2':['i2','j2'],
        'f2':['k2','l2'],
        'g2':['m2','n2'],
        'h2':['o2','p2'],
    }
};

As you can see all the items of the first array (arr) are arrays and it's item in these arrays are strings or numbers or both.
One of the examples I have tried is the following:

var obj = {};
$.each(arr,function(a)
{
    obj[a[0]][a[1]] = a.slice(2);
});

But it produces nothing.
Can someone help me out?

Answer 1

You could use reduce and destructuring like this:

 var arr = [ ['a1','b1','c1','d1'], ['a1','e1','i1','j1'], ['a1','f1','k1','l1'], ['a1','g1','m1','n1'], ['a1','h1','o1','p1'], ['a2','b2','c2','d2'], ['a2','e2','i2','j2'], ['a2','f2','k2','l2'], ['a2','g2','m2','n2'], ['a2','h2','o2','p2'] ]; const newArray = arr.reduce((acc, [key, key2, ...rest]) => { acc[key] = acc[key] || {}; acc[key][key2] = rest return acc; }, {}) console.log(newArray) 

Answer 2

You are on right track. Just the function usage was wrong. I have reused the code and updated it to make it work fine. For $.each function, the first value is the index ( docs ) which was the main cause for error.

I have update the code and it works fine.

 var arr = [ ['a1','b1','c1','d1'], ['a1','e1','i1','j1'], ['a1','f1','k1','l1'], ['a1','g1','m1','n1'], ['a1','h1','o1','p1'], ['a2','b2','c2','d2'], ['a2','e2','i2','j2'], ['a2','f2','k2','l2'], ['a2','g2','m2','n2'], ['a2','h2','o2','p2'] ]; obj = {} $.each(arr,function(index) { obj[arr[index][0]] = obj[arr[index][0]] || {} obj[arr[index][0]][arr[index][1]] = arr[index].slice(2); }); console.log(obj) 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> 

Note: The solution is specific for above requirement. However, it can be generalized as well using recursion.

Hope it helps. Revert for any doubts/clarifications.

Answer 3

使用Lodash库中的reduce可以执行以下操作，其中arr是您的输入数组。

_.reduce(arr, function(acc, val) { var k1 = val[0], k2 = val[1], val = val.slice(2); acc[k1] = acc[k1] || {}; acc[k1][k2] = val; return acc; }, {});

Answer 4

Here's a simple example working for a list of lists (as per your examples), with the min size of leaf arrays being passed as parameter (in your case set to 2).

The mapping extracts a key and accumulates arrays, while the normalizing reduces the arrays recursively, until a satisfying result has been reached.

 var arr = [ ['a1','b1','c1','d1'], ['a1','e1','i1','j1'], ['a1','f1','k1','l1'], ['a1','g1','m1','n1'], ['a1','h1','o1','p1'], ['a2','b2','c2','d2'], ['a2','e2','i2','j2'], ['a2','f2','k2','l2'], ['a2','g2','m2','n2'], ['a2','h2','o2','p2'] ]; console.log(transform(arr, 2)); function transform(input, minSize) { return normalize(map(input, {}), minSize); function map(input, result) { for (var ii = 0; ii < input.length; ii++) { var row = input[ii]; if (row.length == 0) { continue; } var first = row[0]; var list = result[first] || (result[first] = []); list.push(cdr(row)); } return result; } function normalize(result, minSize) { for (var key in result) { var list = result[key]; if (list.length == 0) { continue; } var first = list[0]; if (list.length == 1 && first.length <= minSize) { result[key] = first; continue; } result[key] = transform(list, minSize); } return result; } function cdr(list) { var result = []; for (var ii = 1; ii < list.length; ii++) { result.push(list[ii]); } return result; } }