在新标签页和超时中打开网页

Question

I am wondering, what is happening to the setTimeout's, setInterval's and other functions that trigger when the DOM is loaded, when I open the webpage in other tab or window. Do they trigger once I actually see the webpage, or they trigger once the DOM is loaded, even in the background? Is this different on different browsers?

Answer 1

At least in Chrome and Opera the callback is executed, even if the page is loaded in the background.

Consider the following HTML

<a href="javascript:openWindow()">Click me!</a>

and the respective JavaScript

function openWindow()
{
    var article = open('');
    focus();

    article.setTimeout(function(){ article.alert("Hello"); }, 3000);
}

(See this fiddle ).

If you click on the link with the Ctrl-Key pressed, Chrome opens a new background tab. Still the alert is shown after 3 seconds. The same beaviour can be observed in Opera. I've tried Edge, too, but it won't open the page in a background tab, hence I cannot tell, if the JS would still be executed.