Open In Sci-Hub Userscript

OpenInSciHub.user.js

// ==UserScript==
// @name        Open In Sci-Hub
// @namespace   Violentmonkey Scripts
// @match       https://sciencedirect.com/*
// @match       https://link.springer.com/article/*
// @match       https://ieeexplore.ieee.org/document/*
// @match       https://www.sciencedirect.com/science/article/*
// @match       https://www.nature.com/articles/*
// @match       https://journals.plos.org/plosone/article?id=*
// @match       https://academic.oup.com/journals/*
// @match       https://www.jstor.org/stable/*
// @match       https://pubmed.ncbi.nlm.nih.gov/*
// @match       https://psycnet.apa.org/*
// @match       https://pubs.acs.org/doi/*
// @grant       GM_xmlhttpRequest
// @version     0.01
// @author      github.com/ifeelagood
// @description Attempts to find PDF on Sci-Hub and opens it in a new tab (based on DOI).
// ==/UserScript==

// TODO implement 404 handling for PDF not found

const scihub = "https://sci-hub.se/"; // change to your preferred scihub domain

function getDOI() {
    // This works for 99% of sites. Otherwise, I have seen many other meta tags containing DOI.

    var doi = document.querySelector('meta[name="citation_doi"]');
    if (doi) { return doi.content; }
    
    var doi = document.querySelector('a[href*="doi.org"]');
    if (doi)
    {
        var matches = doi.href.match(/doi\.org\/(.+)/);
        if (matches) { return matches[1]; }
    }
    
    return null;
}

function getPDFUrl(doi) {
    return new Promise((resolve, reject) => {
        var url = scihub + doi;

        // include via 
        GM_xmlhttpRequest({
            method: "GET",
            url: url,
            onload: function(response) {
                if (response.status === 200 && response.responseText) {
                    var parser = new DOMParser();
                    var doc = parser.parseFromString(response.responseText, "text/html");
                    var pdf = doc.querySelector("#pdf");
                    if (pdf) {
                        // remove protocol and domain if present via object
                        var pdfUrlObj = new URL(pdf.src);
                        var pdfUrl = scihub + pdfUrlObj.pathname + pdfUrlObj.search;


                        resolve(pdfUrl);
                    } else {                        
                        reject("PDF not found.");
                    }
                } else {
                    reject("Error loading page.");
                }
            },
            onerror: function() {
                reject("Request failed.");
            }
        });
    });
}

(function() {
    'use strict';
    var doi = getDOI();
    console.log(`Found DOI: ${doi}`);
    if (doi) {
        getPDFUrl(doi).then(pdfUrl => {
            console.log(`Found PDF: ${pdfUrl}`);
            window.open(pdfUrl, "_blank");

        }).catch(error => {
            console.error(error);
            alert("PDF not found on Sci-Hub :(");
        });
    }

})();