There is a TypeScript syntax often seen in some libraries like this:
type AriaRole = 'alert' | 'tree' | 'treegrid' | 'treeitem' | (string & {});
Can someone explain the meaning of string & {}?
It represents a string combined with an object.
Does this concept make sense or is it considered a hack?
It may seem odd at first glance, as the type in question is essentially a string.
However, if you were to specify it as
'alert' | 'tree' | 'treegrid' | 'treeitem' | stringstring. This would result in limited autocomplete suggestions when writing code like this:
let role: AriaRole = 'a
In this case, TypeScript would only recognize AriaRole as a basic string, providing generic autocomplete options without knowledge of the specific values. On the other hand, using string & {} prevents the simplification to string, allowing for enhanced autocomplete suggestions such as 'alert' or 'tree', while still permitting any other string input.
Ultimately, structuring the type in this manner appears to encourage certain strings through autocomplete suggestions, while also making these preferred strings visible upon hovering over the type name.
To @AlekseyL & @kaya3
Here is how you can use the (string & {}) implementation:
type Style = 'bold'|'italic'|'underline'|(string & {})
interface TextProps {
style? : Style
}
export default function TextComponent(props: TextProps) => ....
<TextComponent style='bold' /> // choose from the pre defined styles
<TextComponent style='customStyle' /> // or use a custom style name
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