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