今日头条前端编程题

var p=0;
  var l=2;
  var str = new String("hello world");
  document.writeln(str+"<br />");
  document.writeln(str.replace(str.substr(p,l),strReverse(str.substr(p,l),"")));
  function strReverse(str1,str2){
    var length = str1.length;
    for(var i=length-1;i>=0;i--){
      str2+=str1.charAt(i);
    }

    return str2;
  }

var p=0;
var l=2;
var str = new String("hello world");
document.writeln(str+"<br />");
document.writeln(str.replace(str.substr(p,l),strReverse(str.substr(p,l),"")));
function strReverse(str1,str2){
var length = str1.length;
for(var i=length-1;i>=0;i--){
str2+=str1.charAt(i);
}
return str2;
}

  var n = 7;
  var s = 2;
  var l=6;
   var songNum = Math.floor((l+1)/(s+1)) >n?n:Math.floor((l+1)/(s+1));
   if(songNum % 13 == 0){
     songNum -=1;
   }

   cdNum =Math.ceil( n/songNum );
   if( (n%songNum) !=0 && (n%songNum)%13==0 && (songNum-(n%songNum))==1 ){
     cdNum+=1;
   }
   document.writeln(cdNum);