hack6.js

Ajax.Hacks,快来看啊

/* This file uses ajax_hacks4.html */
var request;
var symbol;   //will hold the stock symbol
var numberOfShares;

function getStockPrice(sym,shs){
    if(sym && shs){
        symbol=sym;
        numberOfShares=shs;
        var url="http://www.parkerriver.com/s/stocks?symbol="+sym;   //www.parkerriver.com
        httpRequest("GET",url,true);
    }
}

//event handler for XMLHttpRequest
function handleResponse(){
    var statusMsg="";
    try{
        if(request.readyState == 4){
            if(request.status == 200){
                /*Check if the return value is actually a number. If so, multiple by the number
           of shares and display the result*/
                var stockPrice = request.responseText;

                try{
                    if(isNaN(stockPrice)) { throw new Error(
                            "The returned price is an invalid number.");}

                    if(isNaN(numberOfShares)) { throw new Error(
                            "The share amount is an invalid number.");}
                    var info = "Total stock value: $"+  calcTotal(stockPrice);
                    displayMsg(document.getElementById("msgDisplay"),info,"black");
                    document.getElementById("stPrice").style.fontSize="0.9em";
                    document.getElementById("stPrice").innerHTML ="price: "+stockPrice;
                } catch (err) {
                    displayMsg(document.getElementById("msgDisplay"),"An error occurred: "+
                                                                     err.message,"red");
                }
            } else {
                //request.status is 503  if the application isn't available; 500 if the application has a bug
                alert("A problem occurred with communicating between the XMLHttpRequest object and the server program.");
            }
        }//end outer if
    } catch (err)   {
        alert("It does not appear that the server is available for this application. Please"+
              " try again very soon. \nError: "+err.message);

    }
}

/* Initialize a Request object that is already constructed */
function initReq(reqType,url,bool){
    try{
        /* Specify the function that will handle the HTTP response */
        request.onreadystatechange=handleResponse;
        request.open(reqType,url,bool);
        request.send(null);
    } catch (errv) {

        alert(
                "The application cannot contact the server at the moment. Please try again in a few seconds."+
                " send caused the prob.");
    }
}

/* Wrapper function for constructing a Request object.
 Parameters:
  reqType: The HTTP request type such as GET or POST.
  url: The URL of the server program.
  asynch: Whether to send the request asynchronously or not. */
function httpRequest(reqType,url,asynch){
    //Mozilla-based browsers
    if(window.XMLHttpRequest){
        request = new XMLHttpRequest();
    } else if (window.ActiveXObject){
        request=new ActiveXObject("Msxml2.XMLHTTP");
        if (! request){
            request=new ActiveXObject("Microsoft.XMLHTTP");
        }
     }
    //the request could still be null if neither ActiveXObject
    //initializations succeeded
    if(request){
       initReq(reqType,url,asynch);
    }  else {
        alert("Your browser does not permit the use of all "+
        "of this application's features!");}
}

function calcTotal(price){
    return stripExtraNumbers(numberOfShares * price);
}
/*Strip any characters beyond a scale of four characters past the decimal point, as in
12.3454 */
function stripExtraNumbers(num) {
    //check if the number's already okay
    //assume a whole number is valid
    var n2 = num.toString();
    if(n2.indexOf(".") == -1)  { return num; }
    //it has numbers after the decimal point,
    //reduce the number after the decimal point to 4
    //we use parseFloat if strings are passed into the method
    if(typeof num == "string") {
      num = parseFloat(num).toFixed(4);
    } else {
       num = num.toFixed(4);
    }
    //strip any extra zeros
    return parseFloat(num.toString().replace(/0*$/,""));
}

function displayMsg(div,bdyText,txtColor){
    //reset DIV content
    div.innerHTML="";
    div.style.backgroundColor="yellow";
    div.style.color=txtColor
    div.innerHTML=bdyText;
}