问题
Is it possible through jQuery (or plain javascript) to test if a webpage on another domain is available? I tried getting the response headers with an ajax-call but I get an error no matter what site outside my own domain I test.
So do I really need a proxy script on my server or would I be able to skip that request?
回答1:
Yes, you need to use a proxy script on your server. JavaScript cannot be used in a browser to request resources across domains, as per the same-origin policy.
回答2:
Is it possible through jQuery (or plain javascript) to test if a webpage on another domain is available?
Due to same origin policy restriction you need a proxy/bridge on your server unless the remote server implements JSONP which obviously we cannot assume for the general case.
回答3:
You can create an <img> tag that points to an existing image on the external domain.
If the onerror event fires, image, and perhaps the entire site, is down.
If it fires after 5 seconds or so, it probably timed out, so the entire site is likely to be down.
来源：https://stackoverflow.com/questions/5573360/test-url-availability-with-javascript