js关于字符长度限制的问题示例探讨

var fun = function(str){
var preg = new RegExp("[/u4e00-/u9fa5]+","gi");
var preg2 = new RegExp("[^/u4e00-/u9fa5]","gi");
var count = 0;
for(var i=0;i<str.length;i++){
if(preg.test(str[i])){
count = count+2;
}else{
count = count+1;
}
}
return count;
}