docs/libs/typescript.js
function tryExtractTypeScriptExtension(fileName) {
        return ts.find(ts.supportedTypescriptExtensionsForExtractExtension, function (extension) { return ts.fileExtensionIs(fileName, extension); });
    }
function tryExtractTypeScriptExtension(fileName) {
        return ts.find(ts.supportedTypescriptExtensionsForExtractExtension, function (extension) { return ts.fileExtensionIs(fileName, extension); });
    }
function tryExtractTypeScriptExtension ( fileName ) { return ts . find ( ts . supportedTypescriptExtensionsForExtractExtension , function ( extension ) { return ts . fileExtensionIs ( fileName , extension ) ; } ) ; }
Return ".ts", ".d.ts", or ".tsx", if that is the extension.
Return . ts . d . ts or . tsx if that is the extension .