JS arrays: how to compare two and create third

Question

It's my first post here :-)

Please, Can you a advice on this:

I have an object and an Array:

activeItems = {
    itemId: ["itemid1", "itemid2", "itemid3", "itemid4", "itemid5", "itemid6", "itemid7", "itemid8", "itemid9", "itemid10"],
    price: ["10.50", "22.10", "13.40", "11", "1100", "500", "100", "400", "500", "20"]
};
selectItems = ["itemid3", "itemid8", "itemid9"];

In the activeItems object price[0] represents the price for itemId[0].

All the prices are in correct order to represent prices for all item ids.

Now, I would like to create a new object with prices for the selecteItems array.

It should look like this:

newObject = {
     itemId: ["itemid3","itemid8","itemid9"],
     price: ["13.40", "400", "500"]
};

Basically, I'm looking for a formula that creates new object for selectedItems out of activeItems and adds prices arrays for them.

Thank you in advance!

Why don't you fix your data so it's easier to work with, like `{itemi1: 10.50, itemid2: 22.10, ...}`? — Barmar, Apr 21 '18 at 10:17
@Barmar maybe that data is needed in that same structure as mentioned by the OP. Maybe in a chart or something similar that requires such structure — Ankit Agarwal, Apr 21 '18 at 10:25
Maybe because I'm a beginner :) It will have 3000+ items and prices. Is it ok? Can you explain your method? You suggestt to use an object rather than two arrays in object? — PAyTEK, Apr 21 '18 at 10:29

score 2 · Accepted Answer · answered Apr 21 '18 at 10:22

Use a forEach loop and get the index of items from activeItems.itemId which can be used to get the corresponding price value from activeItems.price.

var activeItems = {
      itemId: ["itemid1", "itemid2", "itemid3", "itemid4", "itemid5", "itemid6", "itemid7", "itemid8", "itemid9", "itemid10"],
      price: ["10.50","22.10","13.40","11","1100","500","100","400","500","20"]
};

var selectItems = ["itemid3","itemid8","itemid9"];

var itemId = [];
var price = [];
selectItems.forEach(function(item){
  var index = activeItems.itemId.indexOf(item);
  itemId.push(item);
  price.push(activeItems.price[index]);
});

var newObject = {
  itemId: itemId,
  price : price
};

console.log(newObject);

This is exactly what I needed! Thank you Ankit! – PAyTEK Apr 22 '18 at 10:29 — PAyTEK, Apr 22 '18 at 10:29

score 0 · Answer 2 · answered Apr 21 '18 at 10:18

0

Maybe this is what you need: Key value arrays:

var myArray = {"itemid3": "13.40", "itemid8": "400", "itemid9": "500"};

And you add new items like this:

myArray = [];
myArray.itemid15 = "300";

answered Apr 21 '18 at 10:18

Charis Moutafidis

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score 0 · Answer 3 · answered Apr 21 '18 at 10:25

Use the array reduce function

var activeItems = {
  itemId: ["itemid1", "itemid2", "itemid3", "itemid4", "itemid5", "itemid6", "itemid7", "itemid8", "itemid9", "itemid10"],
  price: ["10.50", "22.10", "13.40", "11", "1100", "500", "100", "400", "500", "20"]
};

var selectItems = ["itemid3", "itemid8", "itemid9"];
 
var newObject = selectItems.reduce(function(acc, curr, index) {
  // acc is the object passes as an argument
  // curr is current element
  // in this case curr will be "itemid3", "itemid8", "itemid9" ..so on
  acc.itemId.push(curr);
  // in next step get the index of the itemId3 etc from the original array
   // use this index to get the value from activeItems .price
  acc.price.push(activeItems.price[activeItems.itemId.indexOf(curr)])
  return acc;

}, {

  itemId: [],
  price: []
});
console.log(newObject)

JS arrays: how to compare two and create third

3 Answers3