JavaScript Object Merge and Clone for Client or Server side

npm install upmerge --save

If you do not use npm you can just download build/upmerge.js file from this repository and include it in your project.

Let's assume that you have two objects

var obj1 = {
	a: 'Hi',
	b: 'World',
	c: {
		a: 'Alpha',
		b: 'Beta'
	}
};

var obj2 = {
	a: 'Hello',
	c: {
		g: 'Gamma',
		d: 'Delta'
	},
	d: 'Wow'
};

You merge them with function merge(), using set of options.

The values shown below are defaults so if you do not want to change anything - you can skip options argument, it is optional.

var options = {
	
	// Clone obj1 so it will not be changed during merge
	clone: true,
	
	// Recursive `deep` merge - `all` object levels will be merged in opposite to `first-level merge`
	deep: true,
	
	// Only replace keys/values present in first object OR `return null` if second object contains
	// key that does not exist in obj1
	replaceOnly: false
};

Now, merging:

Client side

<script type="text/javascript">
	var resultObj = upmerge.merge(obj1, obj2, options);
	console.log(resultObj);
</script>

Server side

var upmerge = require('upmerge');
var resultObj = upmerge.merge(obj1, obj2, options);
console.log(resultObj);

The result will be:

{
	a: 'Hello',
	b: 'World',
	c: {
		a: 'Alpha',
		b: 'Beta',
		g: 'Gamma',
		d: 'Delta'
	},
	d: 'Wow'
}

You can use this library not just for merging but also for simple cloning JavaScript objects

var clonedObj = upmerge.clone(origObj);

The 'replaceOnly' mode

If you specify replaceOnly: true in an options argument - your result object will get only those values from merging object (obj2) that stored under existing in base object (obj1) keys. If someone will try to merge new keys into object - the merge() function will return null (merge fail). It is extremely useful when, for instance, you have a reference config (self-documenting, showing all the possible options) in your project and you want to let users to change described config properties only but not to add new ones (since if it is not described in reference config - it is not supported).

Clone or download the repository, go to directory tests and run bower install it will install testing framework qunit then just open tests/index.html in your browser.

Little bit more information about test cases structure you will find in cases.js.

The end