What does a spread operator do when it stands on its own with noting else in a line of code?

Question

Playing around with alpine.js and livewire I came across the following construction and I can't really figure out what it does

<div x-data="readConfig( { selectedKey: @entangle('filteredLocation') })" x-init="fetchOptions()"> 

and than in the script:

function readConfig(entangle) {
    
    return {
        ...entangle,
        filter: '',
       fetchOptions(){... }, 
        ...

The code works fine but I can't figure out what "...entangle" does in this case where it stands on its own in an object literal