142 lines
4.2 KiB
JavaScript
142 lines
4.2 KiB
JavaScript
// https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types#JavaScript_types
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export const redundantScriptTypes = new Set([
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'application/javascript',
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'application/ecmascript',
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'application/x-ecmascript',
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'application/x-javascript',
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'text/javascript',
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'text/ecmascript',
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'text/javascript1.0',
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'text/javascript1.1',
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'text/javascript1.2',
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'text/javascript1.3',
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'text/javascript1.4',
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'text/javascript1.5',
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'text/jscript',
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'text/livescript',
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'text/x-ecmascript',
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'text/x-javascript'
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]);
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// https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#missing-value-default
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const missingValueDefaultAttributes = {
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'form': {
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'method': 'get'
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},
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input: {
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type: 'text'
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},
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button: {
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// https://html.spec.whatwg.org/multipage/form-elements.html#attr-button-type
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type: 'submit'
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},
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'script': {
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'language': 'javascript',
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'type': attrs => {
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for (const [attrName, attrValue] of Object.entries(attrs)) {
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if (attrName.toLowerCase() !== 'type') {
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continue;
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}
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return redundantScriptTypes.has(attrValue);
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}
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return false;
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},
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// Remove attribute if the function returns false
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'charset': attrs => {
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// The charset attribute only really makes sense on “external” SCRIPT elements:
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// http://perfectionkills.com/optimizing-html/#8_script_charset
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return !attrs.src;
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}
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},
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'style': {
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'media': 'all',
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'type': 'text/css'
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},
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'link': {
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media: 'all',
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'type': attrs => {
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// https://html.spec.whatwg.org/multipage/links.html#link-type-stylesheet
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let isRelStyleSheet = false;
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let isTypeTextCSS = false;
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if (attrs) {
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for (const [attrName, attrValue] of Object.entries(attrs)) {
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if (attrName.toLowerCase() === 'rel' && attrValue === 'stylesheet') {
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isRelStyleSheet = true;
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}
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if (attrName.toLowerCase() === 'type' && attrValue === 'text/css') {
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isTypeTextCSS = true;
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}
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}
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}
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// Only "text/css" is redudant for link[rel=stylesheet]. Otherwise "type" shouldn't be removed
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return isRelStyleSheet && isTypeTextCSS;
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}
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},
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// See: https://html.spec.whatwg.org/#lazy-loading-attributes
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img: {
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'loading': 'eager',
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// https://html.spec.whatwg.org/multipage/embedded-content.html#dom-img-decoding
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decoding: 'auto'
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},
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iframe: {
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'loading': 'eager'
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},
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// https://html.spec.whatwg.org/multipage/media.html#htmltrackelement
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track: {
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kind: 'subtitles'
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},
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textarea: {
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// https://html.spec.whatwg.org/multipage/form-elements.html#dom-textarea-wrap
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wrap: 'soft'
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},
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area: {
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// https://html.spec.whatwg.org/multipage/image-maps.html#attr-area-shape
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shape: 'rect'
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}
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};
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const tagsHaveMissingValueDefaultAttributes = new Set(Object.keys(missingValueDefaultAttributes));
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/** Removes redundant attributes */
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export function onAttrs() {
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return (attrs, node) => {
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if (!node.tag) return attrs;
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const newAttrs = attrs;
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if (tagsHaveMissingValueDefaultAttributes.has(node.tag)) {
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const tagRedundantAttributes = missingValueDefaultAttributes[node.tag];
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for (const redundantAttributeName of Object.keys(tagRedundantAttributes)) {
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let tagRedundantAttributeValue = tagRedundantAttributes[redundantAttributeName];
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let isRemove = false;
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if (typeof tagRedundantAttributeValue === 'function') {
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isRemove = tagRedundantAttributeValue(attrs);
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} else if (attrs[redundantAttributeName] === tagRedundantAttributeValue) {
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isRemove = true;
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}
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if (isRemove) {
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delete newAttrs[redundantAttributeName];
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}
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}
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}
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return newAttrs;
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};
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}
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