45 lines
1.7 KiB
JavaScript
45 lines
1.7 KiB
JavaScript
/**
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* Loads a script from a specific URL. React Native cannot load a JS
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* file/resource/URL via a <script> HTML element, so the implementation
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* fetches the specified <tt>url</tt> as plain text using {@link fetch()} and
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* then evaluates the fetched string as JavaScript code (using {@link eval()}).
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*
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* @param {string} url - The absolute URL from which the script is to be
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* (down)loaded.
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* @returns {void}
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*/
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export function loadScript(url) {
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return new Promise((resolve, reject) => {
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// XXX The implementation of fetch on Android will throw an Exception on
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// the Java side which will break the app if the URL is invalid (which
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// the implementation of fetch on Android calls 'unexpected url'). In
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// order to try to prevent the breakage of the app, try to fail on an
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// invalid URL as soon as possible.
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const { hostname, pathname, protocol } = new URL(url);
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// XXX The standard URL implementation should throw an Error if the
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// specified URL is relative. Unfortunately, the polyfill used on
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// react-native does not.
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if (!hostname || !pathname || !protocol) {
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reject(`unexpected url: ${url}`);
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return;
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}
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fetch(url, { method: 'GET' })
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.then(response => {
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switch (response.status) {
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case 200:
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return response.responseText || response.text();
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default:
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throw response.statusText;
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}
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})
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.then(responseText => {
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eval.call(window, responseText); // eslint-disable-line no-eval
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})
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.then(resolve, reject);
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});
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}
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