Javascript函数可打开多个链接（如果存在）

Question

I am looking for a solution to the following scenario:

I'd like to write a script that opens a new window with a specified link (ex: http://yadayada.org/customer#.pdf ). With the same function (or click) I'd like to to also open http://yadayada.org/customer#A.pdf if it exists. Below I have a working sample of a function that works to open the files in 2 new windows. However, I obviously get a blank window if the second location doesn't exist. I'd like the second page to not be opened if the reference does not exist.

function OpenFile() {
    win=window.open('http://yadayada.org/~(student_number).pdf', '_self');
    win2=window.open('http:/yadayada.org/~(student_number)a.pdf', '_blank');
    win.focus();
}

OpenFile();

Answer 1

You will need to check the http status code of the URL using JavaScript to determine if the page exists, and if so then open the link.

If you are using jQuery then it makes life easier: Use javascript to check http status codes

Otherwise you can use plain old JavaScript: How to get HTTP status from JavaScript

[Edit] As mentioned in the comments, this will not work cross-domain.

You could try the following - force the request to be JSONP by adding the ?callback=? parameter to the request, but you need to look at the .fail callback since the pdf is obviously not JSON data. Also, be aware that the entire PDF is downloaded, so there will be a delay for large files.

var url = "http://samplepdf.com/sample.pdf?jsoncallback=?";
$.getJSON(url)
    .fail(function( jqxhr, textStatus, error ) {
        if (jqxhr.status == 200) {
            console.log("request document found success");
        }
    })

"Working" Demo: http://jsfiddle.net/WmHjs/

I would try and make the call server side if you require cross-domain checking.