Return new array of objects based on several properties of existing array of objects

Question

I am breaking my head trying to figure how to achieve what I need. My initial array of objects is 70k objects with 15 attributes each. Through filtering and mapping, I have gotten the data set down to what I think are the relevant parts. I need to return a new array of objects based on each of the 4 properties of each object, with their being duplicate id's and different levels for each code. My filtered data looks like so.

const arr = [{id: "12345", level: "1", current: "Y", code: "1"}, 
             {id: "12345", level: "0", current: "N", code: "1"},
             {id: "54321", level: "1", current: "N", code: "201"},
             {id: "54321", level: "2", current: "Y", code: "201"}, 
             {id: "54321", level: "3", current: "N", code: "201"},
             {id: "54321", level: "0", current: "Y", code: "401"},
             {id: "54321", level: "1", current: "N", code: "401"},
             {id: "54321", level: "3", current: "N", code: "201"},
             {id: "54321", level: "0", current: "N", code: "301"},
             {id: "121212", level: "0", current: "N", code: "3"},
             {id: "121212", level: "1", current: "N", code: "3"}]

What I need to achieve is for each id for any current of Y for each code, I need to find the max level for that code. So for the example above the resulting output would be an array of objects like so:

const result = [{id: "12345", max: "1", code: "1"}, 
                {id: "54321", max: "3", code: "201"},
                {id: "54321", max: "1", code: "401"}]

I'm not even sure if what I want is possible, or if I'm thinking about it the wrong way. I have been racking my brain all morning trying to figure out a solution.

if " for any current of Y" then shouldn't ihe max values be 1,0,2 instead of 1,3,1 ? — mickl
– mickl, Commented Aug 9, 2018 at 17:23
@mickl I may have worded it wrong, but for any code that has a 'Y' for each id I need to find the max of that code for the id. I need the max level for each code that has a 'Y' — kemotoe
– kemotoe, Commented Aug 9, 2018 at 17:45

mickl · Accepted Answer · 2018-08-09 17:51:14Z

2

You can use .filter() and .map() to get initial values based on Y and then .reduce() to get max values:

const arr = [{id: "12345", level: "1", current: "Y", code: "1"}, 
             {id: "12345", level: "0", current: "N", code: "1"},
             {id: "54321", level: "1", current: "N", code: "201"},
             {id: "54321", level: "2", current: "Y", code: "201"}, 
             {id: "54321", level: "3", current: "N", code: "201"},
             {id: "54321", level: "0", current: "Y", code: "401"},
             {id: "54321", level: "1", current: "N", code: "401"},
             {id: "54321", level: "3", current: "N", code: "201"},
             {id: "54321", level: "0", current: "N", code: "301"},
             {id: "121212", level: "0", current: "N", code: "3"},
             {id: "121212", level: "1", current: "N", code: "3"}]

let initialValues = arr.filter(x => x.current === "Y")
		       .map(x => ({ id: x.id, max: x.level, code: x.code }));

let result = arr.reduce((result,current) => {
	var value = result.find(x => x.id === current.id && x.code === current.code);
	if(!value) return result;
	if(value.max < current.level) {
		value.max = current.level;
	}
	return result;
}, initialValues);

console.log(result);

edited Aug 9, 2018 at 17:51

answered Aug 9, 2018 at 17:22

mickl

50.1k9 gold badges71 silver badges99 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

kemotoe Over a year ago

Works like a charm. Thank you!

baao · Accepted Answer · 2018-08-09 17:36:53Z

2

You could reduce to a Map and take its values

const arr = [{id: "12345", level: "1", current: "Y", code: "1"},
    {id: "12345", level: "0", current: "N", code: "1"},
    {id: "54321", level: "1", current: "N", code: "201"},
    {id: "54321", level: "2", current: "Y", code: "201"},
    {id: "54321", level: "3", current: "N", code: "201"},
    {id: "54321", level: "0", current: "Y", code: "401"},
    {id: "54321", level: "1", current: "N", code: "401"},
    {id: "54321", level: "3", current: "N", code: "201"},
    {id: "54321", level: "0", current: "N", code: "301"},
    {id: "121212", level: "0", current: "N", code: "3"},
    {id: "121212", level: "1", current: "N", code: "3"}];
    
    
const res = arr.reduce((a, b) =>
  b.current === 'Y' ?
  a.set(b.id + b.code, (a.get(b.id + b.code) || {
    level: Number.MIN_SAFE_INTEGER
  }).level < b.level ? b : a.get(b.id + b.code)) :
  a, new Map);
console.log([...res.values()]);

answered Aug 9, 2018 at 17:36

baao

73.5k18 gold badges152 silver badges208 bronze badges

1 Comment

mickl Over a year ago

OP is expecting different result

amrender singh · Accepted Answer · 2018-08-09 17:58:35Z

You can simply achieve a Array.reduce() and Object destructuring. construct a map with each key a combination of id and code. Simply use Object.values() on the map to get the desired result :

const arr = [{id: "12345", level: "1", current: "Y", code: "1"}, {id: "12345", level: "0", current: "N", code: "1"}, {id: "54321", level: "1", current: "N", code: "201"}, {id: "54321", level: "2", current: "Y", code: "201"}, {id: "54321", level: "3", current: "N", code: "201"}, {id: "54321", level: "0", current: "Y", code: "401"}, {id: "54321", level: "1", current: "N", code: "401"}, {id: "54321", level: "3", current: "N", code: "201"}, {id: "54321", level: "0", current: "N", code: "301"}, {id: "121212", level: "0", current: "N", code: "3"}, {id: "121212", level: "1", current: "N", code: "3"}];
             
const result = Object.values(arr.reduce((a,{level,current, ...props})=>{
    a[props.id+"_"+props.code] = a[props.id+"_"+props.code] || props;
    a[props.id+"_"+props.code].max = Math.max((a[props.id+"_"+props.code].max || 0), level);
  return a;
},{}));
console.log(result);

Pavlo · Accepted Answer · 2018-08-09 17:46:17Z

const resultObject = (arr, filter) => arr.reduce((sum, element) => {
  const currentInSum = sum[element.id];
  const filterSatisfied = element.current === filter;
  const isHighestLevel = !currentInSum  || currentInSum.level < element.level;
  if(filterSatisfied && isHighestLevel){
     sum[element.id] = element;
  }
  return sum;
}, {});
const result = Object.values(resultObject(arr, "Y"));

Basically you want to use an object so that you can check whether the element is already added, and if the current level is higher than the one already added, then replace it, if this is the first occurence then just add it to the object.

Lastly, just get all the values from the object to convert it to an array, you don't care about the keys which is the object's id.

This algorithm takes O(n*2) time to execute, since you have to run through arr once, and then you have to convert all the values in the object into an array

Collectives™ on Stack Overflow

Return new array of objects based on several properties of existing array of objects

4 Answers 4

1 Comment

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related