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loadAsset.ts
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loadAsset.ts
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/*
* Copyright 2019 LABOR.digital
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Last modified: 2019.01.22 at 18:02
*/
import {isBrowser} from '../Environment/isBrowser';
import {isNumber} from '../Types/isNumber';
import {isString} from '../Types/isString';
interface LoadJsOptions
{
/**
* The timeout in milliseconds after which the promise should fail
*/
timeout?: number,
/**
* The type of asset to load
*/
type?: 'js' | 'css'
}
const loadedJs: Map<string, Promise<string>> = new Map();
/**
* This helper may be used to load additional javascript or css files
* to the current page. It will return a promise which resolves to the loaded url.
*
* NOTE: Should be called after the document is ready!
*
* @param url
* @param options
*/
export function loadAsset(url: string, options?: LoadJsOptions): Promise<string>
{
if (!isBrowser()) {
throw new Error('loadAsset() only works in browsers!');
}
if (loadedJs.has(url)) {
return loadedJs.get(url)!;
}
const promise = new Promise<string>((resolve, reject) => {
options = options ?? {};
const timeoutTime = isNumber(options.timeout) ? options.timeout : 2000;
const timeout = setTimeout(() => reject('Timeout after ' + timeoutTime + 'ms.'), timeoutTime);
(new Promise<void>(resolve1 => {
const elType = isString(options!.type) && options!.type === 'css' ? 'css' : 'js';
let el;
if (elType === 'css') {
el = document.createElement('link');
el.rel = 'stylesheet';
el.href = url;
} else {
el = document.createElement('script');
el.type = 'text/javascript';
el.src = url;
}
document.head.appendChild(el);
el.onload = () => {
resolve1();
};
el.onerror = () => {
reject('An error occured while loading: "' + url + '"');
};
}).then(() => {
clearTimeout(timeout);
resolve(url);
}));
});
loadedJs.set(url, promise);
return promise;
}