65 lines
2.1 KiB
JavaScript
65 lines
2.1 KiB
JavaScript
// @flow
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/**
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* Default timeout for loading scripts.
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*/
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const DEFAULT_TIMEOUT = 5000;
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/**
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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 {@code url} 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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* @param {number} [timeout] - The timeout in millisecnods after which the
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* loading of the specified {@code url} is to be aborted/rejected (if not
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* settled yet).
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* @param {boolean} skipEval - Whether we want to skip evaluating the loaded content or not.
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* @returns {void}
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*/
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export async function loadScript(
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url: string, timeout: number = DEFAULT_TIMEOUT, skipEval: boolean = false): Promise<any> {
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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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throw new Error(`unexpected url: ${url}`);
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}
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const controller = new AbortController();
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const signal = controller.signal;
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const timer = setTimeout(() => {
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controller.abort();
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}, timeout);
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const response = await fetch(url, { signal });
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// If the timeout hits the above will raise AbortError.
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clearTimeout(timer);
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switch (response.status) {
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case 200: {
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const txt = await response.text();
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if (skipEval) {
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return txt;
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}
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return eval.call(window, txt); // eslint-disable-line no-eval
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}
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default:
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throw new Error(`loadScript error: ${response.statusText}`);
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}
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}
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