merge two objects in lodash

Question

I have two arrays of objects as follows:

$scope.var1 = [{
    "field_name": "fname",
    "mapped_field": "firstName",
    "position": 2
}, {
    "field_name": "lname",
    "mapped_field": "lastName",
    "position": 1
}, {
    "field_name": "email",
    "mapped_field": "Email",
    "position": 1
}];

$scope.final = [{
    "field_name": "fname",
    "mapped_field": "lastName",
    "position": 2
}, {
    "field_name": "lname",
    "mapped_field": "firstName",
    "position": 1
}];

Here I want to replace final one where mapped_field matched with var1's mapped_field and remaining of var1 also merged into final one.

Final should be like this:

$scope.final = [{
    "field_name": "fname",
        "mapped_field": "firstName",
        "position": 2
}, {
    "field_name": "lname",
    "mapped_field": "lastName",
    "position": 1
}, {
    "field_name": "email",
    "mapped_field": "Email",
    "position": 1
}];

Any help will highly be appreciated.

Answer 1

Use the combination of lodash functions: _.forEach and _.assign :

_.forEach($scope.var1, function(varObject) {
    //find object with the same mapped_field
    var finalArrayItem = _.find($scope.final, {mapped_field: varObject.mapped_field});
    if (finalArrayItem) {
        //merge objects
        _.assign(finalArrayItem, varObject);
    } else {
        $scope.final.push(varObject);
    }
});

Link to jsbin

Answer 2

Here's what I came up with:

final = _.map(var1, function(item) {
    return _.assign(
        _.find(final, _.pick(item, 'mapped_field')) || {},
        item
    );
});

Where you're using map() to create the create the new final array. The array that's being mapped is var1 , and we return a new object for each array item. The assign() function is used to override properties in final with properties from var1 .

To map the current final item with it's var1 item, you use find() . The pick() function is handy for constructing the filter object. Here, you say that you want to match against the mapped_field property.

The logical || is necessary for the case where there's no match. For instance, the email object. This will just copy over all the var1 properties into the empty object, and return that.