javascript asp教程第九课--cookies
2018-09-06 13:12
Response Cookies in General:
Well start with the Response Cookies collection. I dont think it could be any easier. You simply put the name of the cookie in the argument. The corresponding value is a string. The only time it gets complicated is when you use keys (which I demonstrate below).
Click Hereto run the script in a new window.
Setting a cookie with ASP is pretty simple. The format is . That value can be either a JavaScript string or an ASP native type such as Request.Form(userEmail).
Response Cookie Keys:
If on the first page of your ASP application Response.Cookies(myOnlyCookie) is set, and subsequently on page two of your application Response.Cookies(myOnlyCookie) is reassigned a second value, then only the second value will remain. The first value is lost in this circumstance.
The solution is to either use multiple cookies or to use multiple Keys in the SAME cookie.
Response.Cookies(thirdCookie)(firstKey)=Heres the first Key. Response.Cookies(thirdCookie)(secondKey)=Heres the second Key.
The Setting of one or more Keys is pretty simple. It follows this format: Response.Cookies(name)(key)=value. Again, the value can either be a JavaScript string or ASP native type. The advantage of using keys is that you can store multiple Key/Value pairs inside the very same cookie.
Request Cookies:
Generally you will find ASP cookie management to be far easier than Client Side JavaScript cookies. Down below is the script that retrieves the cookies.
<%@LANGUAGE=JavaScript%> <% if (Response.Cookies.Count <= 0) { Response.Redirect(script09.asp) } var firstCookie = Request.Cookies(firstCookie); var secondCookie = Request.Cookies(secondCookie); var thirdCookie2Keys = Request.Cookies(thirdCookie)(firstKey) thirdCookie2Keys += + Request.Cookies(thirdCookie)(secondKey); %> <HTML> There are <%=Request.Cookies.Count%> Cookies.<BR> 1) <%=firstCookie%><BR> 2) <%=secondCookie%><BR> 3) <%=thirdCookie2Keys%><BR> <A HREF=script09b.asp>Click Here</A> to see how we would sort cookies if we didnt know their names. </HTML>
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Do I even need to explain firstCookie and secondCookie? Its so easy. However, I will have to have explain the retrieval of Keys in thirdCookie.
We retrieve cookies in almost exactly the same way that we set them, and that goes for Keys as well. If you keep track of your Key names, then retrieving their values is pretty easy.
Deleting Cookies:
To delete a cookie, give it an expiration date in the past. The following is not in our examples, but it would work.
var Yesterday=new Date() Yesterday.setDate(Yesterday.getDate() - 1) myExpire = (Yesterday.getMonth() + 1) + / + Yesterday.getDate() myExpire += / + Yesterday.getFullYear() Response.Cookies(firstCookie).Expires=myExpire
Cookie Crumbs:
What if you lose track of your cookie names? What if you lose your Keys? First of all, dont do that. But secondly, we have options.
We can use a VBScript Function with a for/each loop. We can use Javascripts new Enumerator( ) or we can use a pair of for Loops. We, however, cannot use JavaScripts for/in loop. This means we have to be creative.
<%@LANGUAGE=JavaScript%> <% if (Response.Cookies.Count <= 0) { Response.Redirect(script09.asp) } %> <HTML> <SCRIPT LANGUAGE=VBScript RUNAT=Server> Function forEachCookie() dim x,y,z for each x in Request.Cookies if Request.Cookies(x).HasKeys then for each y in Request.Cookies(x) z = z & x & : & y & = & Request.Cookies(x)(y) & ; next else z = z & x & = & Request.Cookies(x) & ; end if next forEachCookie = z End Function </SCRIPT> <% Response.Write(<STRONG>Lets use a VBScript function to ) Response.Write(sort out the Cookies and Keys.</STRONG><BR>\r) var longCookie = forEachCookie() if (longCookie) { longCookie = longCookie.split(; ) for (i=0;i<=longCookie.length-1;i++) { Response.Write(longCookie[ i ] + <BR>\r) } } Response.Write(<HR>\r) Response.Write(<STRONG>Lets use <I>new Enumerator( )</I> to ) Response.Write(sort out the Cookies and Keys.</STRONG><BR>\r) var myEnum = new Enumerator(Request.Cookies); for (myEnum; !myEnum.atEnd() ; myEnum.moveNext() ) { Response.Write(myEnum.item() + =) n=Request.Cookies(myEnum.item()).Count if (n) { for (o=1;o<=n;o++) { Response.Write(Request.Cookies(myEnum.item())(o) + ) } //Begin alternate method of using Enumerator() Response.Write(<BR>\r<STRONG>OR... </STRONG>) Response.Write(myEnum.item() + =) Response.Write(unescape(Request.Cookies(myEnum.item()))) //End alternate method } else { Response.Write(Request.Cookies(myEnum.item())) } Response.Write(<BR>\r) } Response.Write(<HR>\r) Response.Write(<STRONG>Lets use a pair of JavaScript loops to ) Response.Write(sort out the Cookies and Keys.</STRONG><BR>\r) a=Request.Cookies.Count for (b=1;b<=a;b++) { d = Request.Cookies(b).Count if (d) { for (c=1;c<=d;c++) { Response.Write(Request.Cookies(b)(c) + ) } Response.Write(<BR>\r) } else { Response.Write(Request.Cookies(b) + <BR>\r) } } %> </HTML>
Click Hereto run the script in a new window.
We do the same job three times. You decide for yourself which one you like best. In the first example you can plainly see from the script, I ask a VBScript function to find and break down all the cookies. I then output the data back to the waiting JavaScript variable.
var longCookie = forEachCookie()
What can I say? Dont lose track of your cookies and dont lose track of your Keys. Otherwise you might have to get a VBScript slim jim.
The new Enumerator() is okay. I use Enumerator two different ways; one way fails to capture the Key names, and the other way successfully captures the key names (but it needs unescape() to get the Key values to print normally).
In round three, I use a pair of for loops, but theyre not as functional as for/in would be. (Notice the lack of Key names.)
Misc. Notes:
We didnt use new String( ) in this lesson. But remember, if you want to manipulate the cookie values inside JavaScript functions or methods, then you will need new String().
Also, if you were to use Client Side scripting to locate cookies, you would have noticed that there is an extra cookie. ASP keeps track of its sessions using a cookie.
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