JavaScript - merge two arrays of objects and de-duplicate based on property value

Question

I want to update (replace) the objects in my array with the objects in another array. Each object has the same structure. e.g.

var origArr = [
          


        

Answer 1

This will do what you need:

var origArr = [
  {name: 'Trump', isRunning: true},
  {name: 'Cruz', isRunning: true},
  {name: 'Kasich', isRunning: true}
];

var updatingArr = [
  {name: 'Cruz', isRunning: false},
  {name: 'Kasich', isRunning: false}
];

for (var i = 0; i < updatingArr.length; ++i) {
  var updateItem = updatingArr[i];
  for (var j = 0; j < origArr.length; ++j) {
    var origItem = origArr[j];
    if (origItem.name == updateItem.name) {
      origItem.isRunning = updateItem.isRunning;
      break;    
    }
  }
}

document.write('<pre>' + JSON.stringify(origArr, 0, 4) + '</pre>');

Answer 2

Same as @gevorg answer, but you may want to also add a new object to the original array if no matches are found.

let combinedEvents = origEvents;
for(let i =0; i< newEvents.length; i++){
  let newEvent = newEvents[i];
  for(let j =0; j< origEvents.length; j++){
    let origEvent = origEvents[j];
    if(newEvent.events_id == origEvent.events_id){
      combinedEvents.splice(j,1, newEvent);
      break;
    } else if(j === origEvents.length - 1){
      combinedEvents.push(newEvent);
      break;
    }
  }
}

Answer 3

Using a double for loop and splice you can do it like so:

for(var i = 0, l = origArr.length; i < l; i++) {
    for(var j = 0, ll = updatingArr.length; j < ll; j++) {
        if(origArr[i].name === updatingArr[j].name) {
            origArr.splice(i, 1, updatingArr[j]);
            break;
        }
    }
}

Example here

Answer 4

This version lets you define the selector that defines an object as duplicate.

• forEach iterates over the new data
• findIndex returns an index >= 0 if two selectors are equal. If none are equal, it returns -1
• If there is a duplicate, we use slice to replace the original by the new.
• If there's no duplicate, we push it into the original array.

const origArr = [
  {name: 'Trump', isRunning: true},
  {name: 'Cruz', isRunning: true},
  {name: 'Kasich', isRunning: true}
];

const updatingArr = [
  {name: 'Cruz', isRunning: false},
  {name: 'Kasich', isRunning: false}
];

const mergeArrayOfObjects = (original, newdata, selector = 'key') => {
	newdata.forEach(dat => {
		const foundIndex = original.findIndex(ori => ori[selector] == dat[selector]);
		if (foundIndex >= 0) original.splice(foundIndex, 1, dat);
        else original.push(dat);
	});

	return original;
};

const result = mergeArrayOfObjects(origArr, updatingArr, "name")
console.log('RESULT -->', result)

Answer 5

Here's a solution using underscore:

var result = _.map(origArr, function(orig){
    return _.extend(orig, _.findWhere(updatingArr, {name: orig.name}));
});