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highlighter.js
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highlighter.js
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function highlight()
{
var page_id = (document.querySelector("input[name='parent']") || {}).value;
// Not recognizing this page as a post; exiting.
if (!page_id)
return;
chrome.storage.local.get
(
page_id,
function(result)
{
var old_posts = (result || {})[page_id] || {};
// `posts` will be an array of { "id": ..., "element": ... }
// where `element` is a reference to the `td` element that needs to be styled.
var posts = [].map.call(document.querySelectorAll("td.default"), extract_post_details);
// Throw out posts that we couldn't identify.
posts = posts.filter(function(post) { return post.id; });
// Only mark posts if the page has been visited before (i.e. some entries in `old_posts`)
if (Object.keys(old_posts).length > 0)
{
posts.forEach
(
function(post)
{
var element_class = (post.id in old_posts) ? "hn-old-post" : "hn-new-post";
post.element.className += " " + element_class;
}
);
}
// The data stored is a hash of the post IDs seen on this page.
var update = {};
update[page_id] = posts.reduce
(
function(accumulator, post)
{
accumulator[post.id] = 1;
return accumulator;
},
{}
);
chrome.storage.local.set(update);
}
);
function extract_post_details(element)
{
// The only identifier in the DOM (at the time of this writing) is a permanent
// link to the post. Here, parse that link's href, assuming it's in the form
// "item?id=...".
var identifying_tag = element.querySelector(":scope a[href^='item?']");
if (!identifying_tag)
return {};
var href = identifying_tag.href || "";
var post_id = href.slice(href.lastIndexOf("id=") + 3);
return { "id": post_id, "element": element };
}
}
highlight();