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$ContentAsset
Reference $ContentAsset asset files by name instead of using cumbersome file paths or URLs. $ContentAsset provides sharing, versioning, and access control for all asset files, as well as options for mobile optimization and resizing of image files. You can use $ContentAsset in Lightning components markup and within JavaScript controller and helper code.
Using $ContentAsset in Component Markup
To reference a specific asset file in component markup, use $ContentAsset.yourNamespace__assetName. Orgs without a namespace can use $ContentAsset.assetDeveloperName. Use this syntax regardless of whether an asset is for authenticated or unauthenticated sessions. To reference a content asset within an archive, add pathinarchive as a parameter appended to the basic syntax: $ContentAsset.yourNamespace__assetName + 'pathinarchive=images/sampleImage.jpg'.
Here are a few examples.
Aura component referencing an image in an archive asset file:
Include CSS style sheets or JavaScript libraries in a component using the <ltng:require> tag.
Aura component using an asset file to style a div element:
Aura component displays data from a testDisplayData JavaScript asset file: