var findWords = function(words) {
   
    let res = [] 
    let len1 = /[qwertyuiop]/gi;
    let len2 = /[asdfghjkl]/gi;
    let len3 = /[zxcvbnm]/gi;
     
    for(let item of words) {
       
        let count1 =  len1.test(item)
        let count2 =  len2.test(item)
        let count3 =  len3.test(item)

        if((count1+count2+count3)===1){
         res.push(item)
        }
    }
    return res
};

当输入 findWords(["a","b","c","D","c"])
words[2]的正则总是错的！这是什么原因引起的？
words[2] count3是false,words[4] count3是true。
为什么会这样?