Unique codes

[JS recently re-look at the basis of summarizing some good code I hope to give you a reference]

document.getElementById code = var ( "code"); 
function the getCode () { 
    // Prepare a 62 string; 
    // generating a random number; random number can be used as an index of characters; 
    // random index range [0-61] 
    STR = var "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; 
    // random number; 
    var I = 0; 
    var newStr = ""; 
    the while (I <. 4) { 
        var NUM = Math.round (Math.random () * (61-0) +0 ); 
        var curStr STR = [NUM]; 
        // to transfer all characters after the splice caps, and get the new transfer uppercase characters, then verified; 
        var max = newStr.toUpperCase (); 
        var = curStr.toUpperCase maxnew (); 
        IF (max.indexOf (maxnew) === -. 1) { 
            newStr + STR = [NUM]; 
            I ++; 
        } 
    }
    = newStr code.innerHTML; 
} 
the getCode (); 
// the address space assigned to the function code of the onclick attribute; 
code.onclick = the getCode;