12

I have two or more javascript objects. I want to merge them adding values of common properties and then sort them in descending order of values.

e.g.

var a = {en : 5,fr: 3,in: 9}
var b = {en: 8,fr: 21,br: 8}

var c = merge(a,b)

c should then be like this:

c = {
fr: 24,
en: 13,
in:9,
br:8
}

i.e. both objects are merge, values of common keys are added and then keys are sorted.

Here's what I've tried:

var a = {en : 5,fr: 3,in: 9}
var b = {en: 8,fr: 21,br: 8}
c = {}

// copy common values and all values of a to c
for(var k in a){
  if(typeof b[k] != 'undefined'){  
    c[k] = a[k] + b[k]  
  }
  else{ c[k] = a[k]}
}

// copy remaining values of b (which were not common)
for(var k in b){
 if(typeof c[k]== 'undefined'){
  c[k] = b[k]
 }
} 

// Create a object array for sorting
var arr = [];

for(var k in c){
 arr.push({lang:k,count:c[k]})
}

// Sort object array
arr.sort(function(a, b) {
   return b.count - a.count;
})

but I dont think its good. So many loops :( It would be nice if someone can provide a less messy and good code.

Improve this question
7
  • see this link api.jquery.com/jQuery.merge Commented Feb 7, 2012 at 10:57
  • @Dogbert So far I am here, pastebin.com/VQehhcri Commented Feb 7, 2012 at 11:02
  • Plain objects are not sorted. You'll need to go for an array to achieve sorting. Commented Feb 7, 2012 at 11:25
  • None of the answers below is working but I have found a way, but I dont think its good. Please look into that and optimise the code. Here's the pastebin. pastebin.com/nEKB7zAc Commented Feb 7, 2012 at 11:35
  • 1
    @Jashwant your code for sorting is ok, as long as the porpoerties are numbers Commented Feb 7, 2012 at 11:59

4 Answers 4

Reset to default
3

In ES2015+, object properties are ordered (first by ascending numeric keys, then by insertion order for non-numeric keys). This is guaranteed by the specification if you use one of the methods for which iteration order is specified (like Object.getOwnPropertyNames).

In ES2020+, the methods for which enumeration order used to be unspecified are now specified (though environments have been following it for ages anyway).

But you have to be sure that none of the properties are numeric (otherwise, they'll come first, before non-numeric properties, no matter the insertion order).

Use reduce to iterate over each object and create or add to the same property on the accumulator. Then, sort the object's entries, and use Object.fromEntries to transform it into an object with sorted properties. No need for jQuery:

var a = {en : 5,fr: 3,in: 9}
var b = {en: 8,fr: 21,br: 8}
console.log(merge(a, b));

function merge(...objects) {
  const merged = objects.reduce((a, obj) => {
    Object.entries(obj).forEach(([key, val]) => {
      a[key] = (a[key] || 0) + val;
    });
    return a;
  }, {});
  return Object.fromEntries(
    Object.entries(merged).sort(
      (a, b) => b[1] - a[1]
    )
  );
}

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

Comments

2

It is not possible to sort the properties of an object, you can however sort an array:

var merged = $.extend({}, a);
for (var prop in b) {
    if (merged[prop]) merged[prop] += b[prop];
    else merged[prop] = b[prop];
}
// Returning merged at this point will give you a merged object with properties summed, but not ordered.
var properties = [];
for (var prop in merged) {
    properties.push({
        name: prop,
        value: merged[prop]
    });
}
return properties.sort(function(nvp1, nvp2) {
    return nvp1.value - nvp2.value;
});
Improve this answer

6 Comments

I have changed foreach to for and name= prop to name:prop, but it still returns error :(
worked like charm :) I didnt get the code, but this is what I call less messy code. Whats happening here ? return nvp1.value == nvp2.value ? 0 : nvp1.value > nvp2.value ? 1: -1;
@Jashwant I've updated that line to be slightly simpler :). But in the above it uses the conditional operator ? to check for equality of values, if equal it returns 0, otherwise if value1 is greater than value2 it returns 1 otherwise -1.
Your expectation was to get object but you are getting array with this solution,
@PravatMaskey It is not possible to 'sort' properties of an object, you can however sort an array.
|
2

EDIT - i modified the script, this merges the properties if they are of the same type: numbers are summed, strings are concatenated and objects are recursively merged. I didn't include sorting because (quoting this answer Sorting JavaScript Object by property value)

JavaScript objects are unordered by definition (see the ECMAScript Language Specification, section 8.6). The language specification doesn't even guarantee that, if you iterate over the properties of an object twice in succession, they'll come out in the same order the second time.

If you need things to be ordered, use an array and the Array.prototype.sort method.

function is_object(mixed_var) {
    if (Object.prototype.toString.call(mixed_var) === '[object Array]') {
        return false;
    }
    return mixed_var !== null && typeof mixed_var == 'object';
}

function merge(a, b) {
    var cache = {};
    cache = unpackObject(a, cache);
    cache = unpackObject(b, cache);
    return cache;


}

function unpackObject(a, cache) {
    for (prop in a) {
        if (a.hasOwnProperty(prop)) {
            if (cache[prop] === undefined) {
                cache[prop] = a[prop];
            } else {
                if (typeof cache[prop] === typeof a[prop]) {
                    if (is_object(a[prop])) {
                        cache[prop] = merge(cache[prop], a[prop]);
                    } else {
                        cache[prop] += a[prop];
                    }
                }
            }
        }
    }
    return cache;
}

var a = {
    en: 5,
    fr: 3,
    in : 9,
    lang: "js",
    object: {nestedProp: 6}

}
var b = {
    en: 8,
    fr: 21,
    br: 8,
    lang: "en",
    object: {nestedProp: 1, unique: "myne"}
}

var c = merge(a, b);

fiddle here http://jsfiddle.net/vyFN8/1/

Improve this answer

4 Comments

@Jashwant i updated my answer, you have no guarantee that sorting properties will return them in that order.
Yes, I have checked that on other posts of stackoverflow the objects cannot be sorted. But we can create object arrays for them. By the way, you solutions is clean and powerful. Please add code to sort too, so that I can mark it as answer.
@Jashwant as long as your properties are numbers, your sorting algorithm is ok
Your answer is awesome
1

Here is my attempt, which is recursive for nested objects - https://gist.github.com/greenafrican/19bbed3d8baceb0a15fd

// Requires jQuery
// Merge nested objects and if the properties are numbers then add them together, else
// fallback to jQuery.extend() result

function mergeObjectsAdd(firstObject, secondObject) {
    var result = $.extend(true, {}, firstObject, secondObject);
    for (var k in result) {
        if ("object" === typeof result[k]) {
            firstObject[k] = firstObject[k] || {};
            secondObject[k] = secondObject[k] || {};
            result[k] = mergeObjectsAdd(firstObject[k], secondObject[k]);
        } else {
            firstObject[k] = firstObject[k] || 0;
            secondObject[k] = secondObject[k] || 0;
            result[k] = ("number" === typeof firstObject[k] && "number" === typeof secondObject[k]) ? (firstObject[k] + secondObject[k]) : result[k];
        }
    }
    return result;
}
Improve this answer

Comments

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.