lib/extends/_isFile.js
function _isFile (file, callback) {

			if ("undefined" === typeof file) {
				throw new ReferenceError("missing \"file\" argument");
			}
				else if ("string" !== typeof file) {
					throw new TypeError("\"file\" argument is not a string");
				}
				else if ("" === file.trim()) {
					throw new Error("\"file\" argument is empty");
				}
			else if ("undefined" === typeof callback) {
				throw new ReferenceError("missing \"callback\" argument");
			}
				else if ("function" !== typeof callback) {
					throw new TypeError("\"callback\" argument is not a function");
				}
			else {

				lstat(file, (err, stats) => {
					return callback(null, Boolean(!err && stats.isFile()));
				});

			}

		}
function _isFile (file, callback) {

			if ("undefined" === typeof file) {
				throw new ReferenceError("missing \"file\" argument");
			}
				else if ("string" !== typeof file) {
					throw new TypeError("\"file\" argument is not a string");
				}
				else if ("" === file.trim()) {
					throw new Error("\"file\" argument is empty");
				}
			else if ("undefined" === typeof callback) {
				throw new ReferenceError("missing \"callback\" argument");
			}
				else if ("function" !== typeof callback) {
					throw new TypeError("\"callback\" argument is not a function");
				}
			else {

				lstat(file, (err, stats) => {
					return callback(null, Boolean(!err && stats.isFile()));
				});

			}

		}
function _isFile ( file , callback ) { if ( "undefined" === typeof file ) { throw new ReferenceError ( "missing \"file\" argument" ) ; } else if ( "string" !== typeof file ) { throw new TypeError ( "\"file\" argument is not a string" ) ; } else if ( "" === file . trim ( ) ) { throw new Error ( "\"file\" argument is empty" ) ; } else if ( "undefined" === typeof callback ) { throw new ReferenceError ( "missing \"callback\" argument" ) ; } else if ( "function" !== typeof callback ) { throw new TypeError ( "\"callback\" argument is not a function" ) ; } else { lstat ( file , ( err , stats ) => { return callback ( null , Boolean ( ! err && stats . isFile ( ) ) ) ; } ) ; } }
methods 
Async isFile
@param {string} file : file to check
@param {function} callback : operation's result
@returns {void}
methods Async isFile