Question

My Greasemonkey scripts all work in Firefox 3.6, but in Chrome 6 nothing special happens when I load a page that is supposed to trigger them. Here‘s an example script (pasted below) that highlights top comments on Hacker News. Can anyone identify what I’m doing wrong? When I click on the user.js file and install it in Chrome, the installation succeeds.

// ==UserScript==
// @name           Hacker News highlight
// @namespace      http://news.ycombinator.com
// @description    highlights popular comments
// @include        http://news.ycombinator.com/item*

// ==/UserScript==

var GM_JQ = document.createElement('script');
GM_JQ.src = 'http://jquery.com/src/jquery-latest.js';
GM_JQ.type = 'text/javascript';
document.getElementsByTagName('head')[0].appendChild(GM_JQ);

// Check if jQuery's loaded
function GM_wait() {
    if(typeof unsafeWindow.jQuery == 'undefined') { window.setTimeout(GM_wait,100); }
else { $ = unsafeWindow.jQuery; letsJQuery(); }
}

GM_wait();

function letsJQuery() { 

    var maxScore = 0;
    var secBest = 0;
    var min = 0;

    var numComments = 0;
    $(".comhead > span").each(function() {
        numComments = numComments + 1;
        var score = parseInt($(this).text().split(' ')[0]);
        if(score > maxScore) {
            maxScore = score;
        }
        else if(score > secBest) {
            secBest = score;
        }
    });

    min = maxScore - secBest;

    $(".comhead > span").each(function() {
        var score = parseInt($(this).text().split(' ')[0]);

        if(min!=0 && score >= min + 1) {
            $(this).css({'background-color':'#B2D7FB', 'padding':'4px 4px 4px 4px','-moz-border-radius':'3px', '-webkit-border-radius':'3x'});      
        }
    });
}

Answer 1

I have found it easiest to access page resources by injecting my code into the DOM:

// ==UserScript==
// @name           Hacker News highlight
// @namespace      http://news.ycombinator.com
// @description    highlights popular comments
// @include        http://news.ycombinator.com/item*
// @run-at         document-end
// ==/UserScript==

function letsJQuery() {
   // your stuff
}

var jQuery = document.createElement("script"),
    inject = document.createElement("script");

jQuery.setAttribute("type", "text/javascript");
jQuery.setAttribute("src", "http://code.jquery.com/jquery-latest.js");

inject.setAttribute("type", "text/javascript");
inject.appendChild(document.createTextNode("(" + letsJQuery + ")()"));

document.body.appendChild(jQuery);
document.body.appendChild(inject);

The @run-at ensures that the script loads immediately after DOMDocumentReady, just as in Greasemonkey, and I changed your jQuery URL to point to their CDN.