已知有字符串foo="get-element-by-id",写一个function将其转化成驼峰表示法"getElementById" ```js var foo="get-element-by-id"; function combo(foo) { var arr = foo.split("-"); for (var i = 1; i < arr.length; i++) { arr[i] = arr[i].charAt(0).toUpperCase() + arr[i].substr(1, arr[i].length - 1); } foo = arr.join(""); return foo; } alert(combo(foo)); ```