Merging two json array object based on union and intersection

Question

I am trying to merge two json array with objects as element. You may refer to this plunkr file for both json. I have succesfully retrieve the expected final outcome array id, but I do not know how to form back the expected json as below. I am using underscore js for this purpose.

Note: If object exist in newJson and not in currentJson, after merge, it will be inactive state by default.

I am not sure whether I am using the correct approach. This is what I have try:

var newJsonID = _.pluck(newJson, 'id');
var currentJsonID =  _.pluck(currentJson, 'id');
var union = _.union(newJsonID, currentJsonID);
var intersection = _.intersection(currentJsonID, newJsonID);
var final = _.difference(union, _.difference( currentJsonID, intersection);

Expected Final Outcome:

   [
    {
        "id": "12",
        "property1Name": "1"
        "status": "inactive"
    },
    {
        "id": "11",
        "property1Name": "1"
        "status": "inactive"
    },
    {
        "id": "10",
        "property1Name": "1"
        "status": "inactive"
    },
    {
        "id": "9",
        "property1Name": "1"
        "status": "active"
    }
]

where do you get the status from? i mean with the same id? — Nina Scholz
– Nina Scholz, Commented May 18, 2016 at 15:53
@NinaScholz do you mean where do I get the status from expected final outcome? If the id in newJson do exist in currentJson, take the currentJson status of same id, else default to inactive. — vincentsty
– vincentsty, Commented May 18, 2016 at 16:22

Nina Scholz · Accepted Answer · 2016-05-18 17:08:04Z

2

A solution in plain Javascript with two loops and a hash table for lookup.

function update(newArray, currentArray) {
    var hash = Object.create(null);
    currentArray.forEach(function (a) {
        hash[a.id] = a.status;
    });
    newArray.forEach(function (a) {
        a.status = hash[a.id] || 'inactive';
    });
}

var newJson = [{ "id": "12", "property1Name": "1" }, { "id": "11", "property1Name": "1" }, { "id": "10", "property1Name": "1" }, { "id": "9", "property1Name": "1" }],
    currentJson = [{ "id": "10", "property1Name": "1", "status": "inactive" }, { "id": "9", "property1Name": "1", "status": "active" }, { "id": "8", "property1Name": "1", "status": "active" }, { "id": "7", "property1Name": "1", "status": "inactive" }];
   
update(newJson, currentJson);
document.write('<pre>' + JSON.stringify(newJson, 0, 4) + '</pre>');

edited May 18, 2016 at 17:08

answered May 18, 2016 at 16:39

Nina Scholz

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3 Comments

vincentsty Over a year ago

Oops. I have missed out the property1Name in the final expected solution. Basically, new Json could have a lot of property name, eg: property1Name, property2Name etc, while currentJson will have extra 1 property which is status. Based on this solution you give, I have to hard code return { id: a.id, property1Name: a.property1Name, status: hash[a.id] }, which does not seems to be optimal for me as when an extra property is being added in the json (retreive from db), I have to change the code in javascript again or else it will not be reflected. Is there any possible solution to avoid this?

Nina Scholz Over a year ago

would you like to add only the status property to newJson?

vincentsty Over a year ago

basically the final outcome should have all the existing property that is available in newJson plus status.

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