Say you have an object you’d like to conditionally add a member to, here’s a neat little trick to do it with the spread operator.
function createObject(someParam = null) {
return {
param1: 'value',
param2: 'value',
...(someParam ? {someParam} : {} ),
};
}
The spread syntax allows an iterable to expand in places where 0+ arguments are expected. For a more in-depth explanation have a look at this article by Brandon Morelli.
The example is pretty contrived, but what we’re doing here is checking if someParam has a value, then creating an object with it which is copied to the returned object using the spread operator.
If someParam doesn’t have a value, we simple copy an empty object to the returned object.
Notice that the spread part could still be written like this:
...(someParam ? {someParam: someParam} : {} )
But we’re making use of the ES6/ES2015 object shorthand property.
With it, if you want to define an object who’s keys have the same name as the variables passed-in as properties, you can use the shorthand and simply pass the key name as we did above.