30-seconds-of-code/snippets/longestString.md

longestString

Takes an array of strings and returns the longest one. The method also accepts combinations of single strings and string arrays

Uses the rest operator to handle arrays as well as an indefinite amount of single arguments. Strings are compared using Array.reduce().

const longestString = (...strings) => strings.map(str => {
                          if (Array.isArray(str)) {
                            const first = str.shift();
                            strings.concat(str);
                            return first;
                          } else {
                            return str;
                          }
                        }).reduce((a, b) => a.length > b.length ? a : b);

longestString('this', 'is', 'a', 'testcase'); // 'testcase'
longestString(['a', 'ab', 'abc']); // 'abc'
longestString(['a', 'ab', 'abc'], 'abcd'); // 'abcd'