TamperMonkey helper scripts

helpers.js

function htmlToNode(html) {
	const template = document.createElement('template');
	template.innerHTML = html;
	const nNodes = template.content.childNodes.length;
	if (nNodes !== 1) {
		throw new Error(
			`html parameter must represent a single node; got ${nNodes}. ` +
			'Note that leading or trailing spaces around an element in your ' +
			'HTML, like " <img/> ", get parsed as text nodes neighbouring ' +
			'the element; call .trim() on your input to avoid this.'
		);
	}
	return template.content.firstChild;
}

function downloadBlob(filename, blob) {
	const url = window.URL.createObjectURL(blob);
	const link = document.createElement("a");
	link.href = url;
	link.setAttribute("download", filename);
	document.body.appendChild(link);
	link.click();
}

function querySelectorIncludesText (selector, text){
	return Array.from(document.querySelectorAll(selector))
	    .filter(el => el.textContent.includes(text));
}

function findClosestParent (startElement, fn) {
	var parent = startElement.parentElement;
	if (!parent) return undefined;
	return fn(parent) ? parent : findClosestParent(parent, fn);
}

function xhrPatcher(xhr, patches) {

    async function doPatch(x) {
        if (x.__tmPatched) return;

        for (const patch of patches) {
            if (!patch.match || patch.match(x.__tmUrl, x.__tmMethod, x.__tmData, x)) {
                if (patch.readyState == null || patch.readyState == x.readyState) {
                    const res = await patch.patch(x.response, x.responseType, x);
                    if (res !== undefined) {
                        Object.defineProperty(x, 'response', { writable: true });
                        x.response = res;

                        if (typeof res == "string") {
                            Object.defineProperty(x, 'responseText', { writable: true });
                            x.responseText = res;
                        }
                    }
                    x.__tmPatched = true;
                }
                //console.log(`Monkey patched ${x.__tmMethod} ${x.__tmUrl}:`, x.response);
            }
        }
    }

    const originalAddEventListener = xhr.addEventListener;

    xhr.addEventListener = function(type, listener, options) {
        if (type == 'readystatechange') {
            var patchedListener = async function(event) {
                doPatch(this);
                listener.call(this, event);
            };

            originalAddEventListener.call(this, type, patchedListener, options);
            this.__tmListenerPatched = true;
        } else {
            originalAddEventListener.call(this, type, listener, options);
        }
    };

    var originalOpen = xhr.open;
    xhr.open = function (method, url) {
      this.__tmUrl = url;
      this.__tmMethod = method;
      return originalOpen.apply(this, arguments);
    };

    // Capture request before any network activity occurs:
    var originalSend = xhr.send;
    xhr.send = function(data) {
        this.__tmData = data;

        if (this.onreadystatechange) {
            var originalRSC = this.onreadystatechange;
            if (originalRSC) {
                // "onreadystatechange" exists. Monkey-patch it
                this.onreadystatechange = async function() {
                    //console.log("onreadystatechange", this);
                    await doPatch(this);
                    return originalRSC.apply(this, arguments);
                };
            }
        } else if (!this.__tmListenerPatched) {
            this.addEventListener("readystatechange", function() {});
        }

        var originalLoad = this.onload;
        if (originalLoad) {
            // "onload" exists. Monkey-patch it
            this.onload = async function() {
                //console.log("onload", this);
                await doPatch(this);
                return originalLoad.apply(this, arguments);
            };
        }

        return originalSend.apply(this, arguments);
    };
}

Example 1

// @require      https://gist.githubusercontent.com/icebob/b662bd73f28816a1716dab0844814a09/raw/61cb547ad44b895fd8d19a86fe15d4797550928b/helpers.js

(function() {
    'use strict';

    xhrPatcher(XMLHttpRequest.prototype, [
        {
            readyState: 4,
            match: (url, method, data, xhr) => {
                //console.log("Matcher", url, method, data);
                return url.startsWith("/graphql");
            },
            patch: async (response, responseType, xhr) => {
                console.log("Patch", response);
                const str = await response.text();
                //console.log("Str", str);
                const json = JSON.parse(str);
                if (json?.data?.me?.name) {
                    json.data.me.name = "Monkey";
                }

                return JSON.stringify(json);
                //return new Blob([JSON.stringify(json)], { type: 'application/json' });
            }
        }
    ]);
})();