Merge objects containing array

Question

How can I merge two objects containing array and other fields using lodash?

For example,

obj1 = {
    name: "abc",
    hobbies: ["reading","cricket"]
}
obj2 = {
    name: "abc2",
    hobbies: ["reading","hockey"]
}
_.merge(obj1, obj2)

// output
{
    name: "abc2",
    hobbies: ["reading","hockey"]
}

this returns an object after merging obj1 into obj2 but without merging the hobbies.

So, you want to overwrite name with obj2, but not overwrite hobbies? — gen_Eric
– gen_Eric, Commented Jan 7, 2015 at 20:17
Your output is just the same as obj2. I'm a little confused at the result you want. — gen_Eric
– gen_Eric, Commented Jan 7, 2015 at 20:23
Name is correct. I want hobbies to be reading, cricket, hockey — vinesh
– vinesh, Commented Jan 7, 2015 at 20:25
_.merge isn't part of underscore.js. Where are you getting that from? — gen_Eric
– gen_Eric, Commented Jan 7, 2015 at 20:31

Bart Jedrocha · Accepted Answer · 2015-01-07 20:44:19Z

3

Underscore.js doesn't have a _.merge function so I'm assuming you're using Lo-Dash. If that's the case, you can use the callback parameter to do what you want

var obj1 = { name: 'abc', hobbies: ['reading', 'cricket'] };
var obj2 = { name: 'def', hobbies: ['reading', 'hockey'] };

var output = _.merge(obj1, obj2, function(a,b) {
    return _.isArray(a) ? _.union(a,b) : undefined;
} );
console.log( output );

// output

{ name: 'def', hobbies: ['reading', 'cricket', 'hockey'] }

EDIT

Working JSFiddle.

answered Jan 7, 2015 at 20:44

Bart Jedrocha

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