A proof of concept script to append aria doc roles based on epub:type

index.js

"use strict";

// Get all the elements with epub:type
// Since querySelectorAll can’t be used with XHTML attributes, 
// we create an array in which we’ll push elements with an epub:type attribute

// Mappings table (epub → role)
var mappings = {
    "abstract":"doc-abstract",
    "acknowledgments":"doc-acknowledgments",
    "afterword":"doc-afterword",
    "appendix":"doc-appendix",
    "biblioentry":"doc-biblioentry",
    "bibliography":"doc-bibliography",
    "biblioref":"doc-biblioref",
    "chapter":"doc-chapter",
    "colophon":"doc-colophon",
    "conclusion":"doc-conclusion",
    "cover":"doc-cover",
    "credit":"doc-credit",
    "credits":"doc-credits",
    "dedication":"doc-dedication",
    "endnote":"doc-endnote",
    "endnotes":"doc-endnotes",
    "epigraph":"doc-epigraph",
    "epilogue":"doc-epilogue",
    "errata":"doc-errata",
    "figure":"figure",
    "footnote":"doc-footnote",
    "foreword":"doc-foreword",
    "glossary":"doc-glossary",
    "glossdef":"definition",
    "glossref":"doc-glossref",
    "glossterm":"term",
    "index":"doc-index",
    "introduction":"doc-introduction",
    "landmarks":"directory",
    "list":"list",
    "list-item":"listitem",
    "noteref":"doc-noteref",
    "notice":"doc-notice",
    "pagebreak":"doc-pagebreak",
    "page-list":"doc-pagelist",
    "part":"doc-part",
    "preface":"doc-preface",
    "prologue":"doc-prologue",
    "pullquote":"doc-pullquote",
    "qna":"doc-qna",
    "referrer":"doc-backlink",
    "subtitle":"doc-subtitle",
    "table":"table",
    "table-row":"row",
    "table-cell":"cell",
    "tip":"doc-tip",
    "toc":"doc-toc",
};

var epubTypes = [].slice.call(document.querySelectorAll("*"))
    // Check if the current element has an epub:type attribute and if element hasn’t a role attribute 
    .filter(el => el.hasAttribute("epub:type") && !el.hasAttribute("role"));

// Init append role="" loop
epubTypes.forEach(element => {
    var roles = element.getAttribute("epub:type") // Get the value for epub:type - in tagsoup HTML, should be epub\\\:type
                .split(" ", 2)// Split the string (we only check 2 = 1 space separator)
                .map(inflection => mappings[inflection]) // check if the value (string) is in the mappings table
                .filter(el => !!el);

    element.setAttribute("role", roles.shift()); // first element since role can only have one value   
});

Very good script.
But wouldn't that be ...
epubTypes.forEach(element... and not epubTypes.forEach(el ?

Thx.

Thanks for the script I helped myself for my project vscode - EpubTools