javascript - JS 跳出嵌套 for 循环

Question

为以下算法问题编写代码，但不知道为什么它不起作用。在调试器之后，我发现 elem 变量永远不会迭代超出“s”。我担心这可能是因为我对如何打破父 for 循环的理解。我读这个问题:Best way to break from nested loops in Javascript?但我不确定我是否做错了什么。

function firstNonRepeatingLetter(s) {
  //input string
  //return first character that doesn't repeat anywhere else.
  //parent for loop points to the char we are analyzing
  //child for loop iterates over the remainder of the string
  //if child for loop doesnt find a repeat, return the char, else break out of the child for loop and cont

 if (s.length == 1) { return s;}

  parent_loop:
  for (var i = 0; i < s.length - 1; i++){ //parent loop
      var elem = s[i];
      child_loop:
      for (var j = i + 1; j < s.length; j++){
          if (elem == s[j]){
            break child_loop;
          }
      }
    return s[i];
    } 
 return "";
}  

console.log(firstNonRepeatingLetter('stress')); // should output t, getting s.

Answer 1

我的建议是使用单个 for 循环而不是使用两个循环。

for( var i = 0; i<s.length - 1;i++) {
    var lastIndex = s.lastIndexOf(s[i]);
    if ( lastIndex == i) {
       return s[i];
    }
}