40 lines
929 B
JavaScript
40 lines
929 B
JavaScript
'use strict';
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const { URL } = require('url');
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/**
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* Get unit from value node
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*
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* Returns `null` if the unit is not found.
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*
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* @param {string} urlString
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*/
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module.exports = function (urlString) {
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let protocol = null;
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try {
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protocol = new URL(urlString).protocol;
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} catch (err) {
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return null;
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}
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if (protocol === null || typeof protocol === 'undefined') {
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return null;
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}
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const scheme = protocol.slice(0, -1); // strip trailing `:`
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// The URL spec does not require a scheme to be followed by `//`, but checking
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// for it allows this rule to differentiate <scheme>:<hostname> urls from
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// <hostname>:<port> urls. `data:` scheme urls are an exception to this rule.
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const slashIndex = protocol.length;
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const expectedSlashes = urlString.slice(slashIndex, slashIndex + 2);
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const isSchemeLessUrl = expectedSlashes !== '//' && scheme !== 'data';
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if (isSchemeLessUrl) {
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return null;
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}
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return scheme;
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};
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