Magento 2: uiElement Maps Default

One Magento uiElement default you don’t need to worry about is the maps default, seen here in uiElement’s source file

#File: vendor/magento/module-ui/view/base/web/js/lib/core/element/element.js
defaults:{
    /* ... */
    maps: {
        imports: {},
        exports: {}
    },    
    /* ... */        
}    

This isn’t a magic default, it’s just the uiElement class setting up a skeleton data structure. Magento uses the .maps property of the instantiated object in the Magento_Ui/js/lib/core/element/links module. The functions in the links module are merged in as methods on your uiElement instantiated object. If you look at links.js, wherever you see owner.maps

#File: vendor/magento/module-ui/view/base/web/js/lib/core/element/links.js
if (data) {
    setData(owner.maps, property, data);
    transfer(owner, data, property, true);
}    

That .maps property is a property on your uiElement. Magento uses the information in maps to keep track of what’s been imported/exported into a uiElement based object. You can see this on the customer listing page with the following console javascript

object = requirejs('uiRegistry').get('customer_listing.customer_listing.listing_top.columns_controls');

console.log(object.maps.import);

For more information on the import/export defaults feature, see the Magento 2: uiClass Data Features article and the Magento Quickies post covering the links default.