underscore js mapping array of objects multiple properties to new array

Question

var items = [{
  //other properties... above
  item_name: [
    [1],
    [2, 3]
  ],
  item_description: [
    [1],
    [3, 4]
  ],
  item_quantity: [
    [1],
    [4, 5]
  ],
  item_value: null,
}, {
  //other properties... above
  item_name: 1,
  item_description: 2,
  item_quantity: 3,
  item_value: 4,
}, {
  //other properties... above
  item_name: [1, 2, 3],
  item_description: [1, 2, 3],
  item_quantity: [1, 2, 3],
  item_value: [1, 2, 3],
}];

var itemList = [];



items.forEach(function(item) {

  if (!_.isArray(item.item_name)) {
    itemList.push({
      name: item.item_name,
      description: item.item_description,
      quantity: item.item_quantity,
      value: item.item_value
    });
  }

  var names = item.item_name ? _.flatten(item.item_name) : [];
  var descriptions = item.item_description ? _.flatten(item.item_description) : [];
  var quantity = item.item_quantity ? _.flatten(item.item_quantity) : [];
  var values = item.item_value ? _.flatten(item.item_value) : [];

  names.forEach(function(name, index) {
    itemList.push({
      name: names[index],
      description: descriptions[index],
      quantity: quantity[index],
      values: values[index]
    });
  })
  

});
console.log(itemList);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.4.1/underscore-min.js"></script>

is there a way I can perform this faster in underscore, to remove all of the flattens?

for each item in the array I am taking

item_name[i]
item_description[i]
item_quantity[i]
item_value[i]

and adding them to the itemList

item properties in items can be [[],[]] or [] or integer or null

currently it is outputting what is expected (unless a name is null and it can skip items) however I do not like all of the loops this is performing and I am wondering if I can make a better use of underscore library

Ismail RBOUH · Accepted Answer · 2016-07-22 19:11:51Z

You can use this:

var myKeys = ['name', 'description', 'quantity', 'value'];
var result = _.flatten(items.map(function(item) {
    return _.zip.apply(_, myKeys.map(function(key) {
        return _.flatten([item['item_'+key]]);
    })).map(function(arr) {
        return _.object(myKeys, arr);
    });
}));

Demo:

var items = [{
    //other properties... above
    item_name: [
        [1],
        [2, 3]
    ],
    item_description: [
        [1],
        [3, 4]
    ],
    item_quantity: [
        [1],
        [4, 5]
    ],
    item_value: null,
}, {
    //other properties... above
    item_name: 1,
    item_description: 2,
    item_quantity: 3,
    item_value: 4,
}, {
    //other properties... above
    item_name: [1, 2, 3],
    item_description: [1, 2, 3],
    item_quantity: [1, 2, 3],
    item_value: [1, 2, 3],
}];
var myKeys = ['name', 'description', 'quantity', 'value'];
var result = _.flatten(items.map(function(item) {
    return _.zip.apply(_, myKeys.map(function(key) {
        return _.flatten([item['item_'+key]]);
    })).map(function(arr) {
    	return _.object(myKeys, arr);
    });
}));
console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.4.1/underscore-min.js"></script>

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