请问我这个函数错在哪，为什么不能运行啊?

Question

function assertEquals(s){

  var arr=s.split('');

if(arr.length<=2){

return s

}else{

var b=arr.legth%2

if(b==0){

return arr[arr.length/2-1]+arr[arr.length/2];

}else{

       arr[Math.floor(arr.length/2)]

      }

}}

我想实现返回函数给定的字符串变量  如果字符串字母偶数个  返回中间两个，如：assertEquals(abcdef)  返回cd

如果函数字符串字母奇数个  返回中间的一个  如  assertEquals(abcde)  返回c

Answer 1

你的错误：var b=arr.legth%2    // 这里的lenth拼写错误，应该是lengtharr[Math.floor(arr.length/2)]    // 这里缺少return。修正后：function assertEquals(s){ var arr=s.split(''); if(arr.length<=2){ return s }else{ var b=arr.length%2 if(b==0){ return arr[arr.length/2-1]+arr[arr.length/2]; }else{ return arr[Math.floor(arr.length/2)] } } }再看我写的，<script> function assertEquals(s){     var middle = parseInt(s.length/2),         isEven = s.length%2==0;     return s.substr(isEven?middle-1:middle, isEven?2:1); } </script>

Answer 2

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Answer 3

检查你标点符号