mirror of
https://github.com/mdn/webextensions-examples.git
synced 2026-04-16 14:28:33 +02:00
37cb9f7a84
* Improve content script injection * Add an error handler for content script injection * Use a guard variable in the content script, instead * Fix comment * Ensure tabID is unchanged; fix image styles * Only inject script once; use CSS to hide page * Display an error when the script can't be executed; document other limitations * Log error on script execute failure
49 lines
1.2 KiB
JavaScript
49 lines
1.2 KiB
JavaScript
(function() {
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/**
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* Check and set a global guard variable.
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* If this content script is injected into the same page again,
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* it will do nothing next time.
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*/
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if (window.hasRun) {
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return;
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}
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window.hasRun = true;
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/**
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* Given a URL to a beast image, remove all existing beasts, then
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* create and style an IMG node pointing to
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* that image, then insert the node into the document.
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*/
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function insertBeast(beastURL) {
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removeExistingBeasts();
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let beastImage = document.createElement("img");
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beastImage.setAttribute("src", beastURL);
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beastImage.style.height = "100vh";
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beastImage.className = "beastify-image";
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document.body.appendChild(beastImage);
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}
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/**
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* Remove every beast from the page.
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*/
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function removeExistingBeasts() {
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let existingBeasts = document.querySelectorAll(".beastify-image");
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for (let beast of existingBeasts) {
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beast.remove();
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}
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}
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/**
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* Listen for messages from the background script.
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* Call "beastify()" or "reset()".
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*/
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browser.runtime.onMessage.addListener((message) => {
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if (message.command === "beastify") {
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insertBeast(message.beastURL);
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} else if (message.command === "reset") {
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removeExistingBeasts();
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}
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});
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})();
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