# Mapping object values from one object to another

I have an object called defaultOptions and a function that accepts as an argument an object called newValues meant to override the values in defaultOptions with its own. The values that are not specified in newValues should remain default.

var configOptions = {
isActive: false,
name: "",
description: "",
category: "",
group: "default"
}

publishOptions: function(newValues){
\$.each(newValues, function(key, value){
if(configOptions.hasOwnProperty(key)){
configOptions[key] = value;
}
else{
configOptions[key] = value;
}
});
console.log(configOptions);
}


For example, if I use this method like so:

var myOptions = {
name: "option one",
category: "the best"
}

publishOptions(myOptions)


I would expect configOptions to look like this:

configOptions = {
isActive: false,
name: "option one",
description: "",
category: "the best",
group: "default"
}


I'm using jQuery's each method to map the values from newValues to configOptions, but I suspect there is a much more succinct and elegant way to do this. I would appreciate any suggestions.

• You can also use ES6 spread syntax like: configOptions = {...configOptions, ...myOptions} – Pavan Jan 31 '19 at 9:37
• This may be true, but what's missing is why you would do this. Is it more efficient? Easier to read? Does it handle edge cases better? Is it more reliable? What is it about the original code that makes you suggest this alternative? – mdfst13 Jan 31 '19 at 11:31

jQuery has extend, which seems to be what you are looking for:

http://api.jquery.com/jquery.extend/

Otherwise, if you don't want to use jQuery at all, you can make a for loop:

var first  = { value: 1, string: "two" };
var second = { value: 2 };

for ( var i in second )
if ( first.hasOwnProperty( i ) )
first[i] = second[i];

first.value == 2; // true


As a side, your if statement isn't doing anything because both cases assign the value to configOptions.

You can use Lodash's merge function:

var defaultConfigOptions = {
isActive: false,
name: "",
description: "",
category: "",
group: "default"
}

var myOptions = {
name: "option one",
category: "the best"
}

var configOptions = _.merge({}, defaultConfigOptions, myOptions)

console.log(configOptions === defaultConfigOptions)
console.log("configOptions: ", configOptions)
console.log("defaultConfigOptions: ", defaultConfigOptions)


And this is what you will get:

See in jsbin: https://jsbin.com/jayihus/edit?js,console,output