83 lines
2.7 KiB
TypeScript
83 lines
2.7 KiB
TypeScript
/**
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* The two parts of a file name - the name itself, and an (optional) extension.
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*
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* The extension does not include the dot.
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*/
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type FileNameComponents = [name: string, extension: string | undefined];
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/**
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* Split a filename into its components - the name itself, and the extension (if
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* any) - returning both. The dot is not included in either.
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*
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* For example, `foo-bar.png` will be split into ["foo-bar", "png"].
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*
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* See {@link fileNameFromComponents} for the inverse operation.
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*/
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export const nameAndExtension = (fileName: string): FileNameComponents => {
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const i = fileName.lastIndexOf(".");
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// No extension
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if (i == -1) return [fileName, undefined];
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// A hidden file without an extension, e.g. ".gitignore"
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if (i == 0) return [fileName, undefined];
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// Both components present, just omit the dot.
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return [fileName.slice(0, i), fileName.slice(i + 1)];
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};
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/**
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* If the file name or path has an extension, return a lowercased version of it.
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*
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* This is handy when comparing the extension to a known set without worrying
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* about case sensitivity.
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*
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* See {@link nameAndExtension} for its more generic sibling.
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*/
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export const lowercaseExtension = (
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fileNameOrPath: string,
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): string | undefined => {
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// We rely on the implementation of nameAndExtension using lastIndexOf to
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// allow us to also work on paths.
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const [, ext] = nameAndExtension(fileNameOrPath);
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return ext?.toLowerCase();
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};
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/**
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* Construct a file name from its components (name and extension).
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*
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* Inverse of {@link nameAndExtension}.
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*/
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export const fileNameFromComponents = (components: FileNameComponents) =>
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components.filter((x) => !!x).join(".");
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/**
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* Return the file name portion from the given {@link path}.
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*
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* This tries to emulate the UNIX `basename` command. In particular, any
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* trailing slashes on the path are trimmed, so this function can be used to get
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* the name of the directory too.
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*
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* The path is assumed to use POSIX separators ("/").
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*/
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export const basename = (path: string) => {
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const pathComponents = path.split("/");
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for (let i = pathComponents.length - 1; i >= 0; i--)
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if (pathComponents[i] !== "") return pathComponents[i];
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return path;
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};
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/**
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* Return the directory portion from the given {@link path}.
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*
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* This tries to emulate the UNIX `dirname` command. In particular, any trailing
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* slashes on the path are trimmed, so this function can be used to get the path
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* leading up to a directory too.
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*
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* The path is assumed to use POSIX separators ("/").
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*/
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export const dirname = (path: string) => {
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const pathComponents = path.split("/");
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while (pathComponents.pop() == "") {
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/* no-op */
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}
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return pathComponents.join("/");
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};
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