wavesurfer.js/src/util/ajax.js

Interactive navigable audio visualization using Web Audio and Canvas

import Observer from './observer';

/**
 * Perform an ajax request
 *
 * @param {Options} options Description
 *
 * @returns {Object} Observer instance
 */
export default function ajax(options) {
    const instance = new Observer();
    const xhr = new XMLHttpRequest();
    let fired100 = false;
    xhr.open(options.method || 'GET', options.url, true);
    xhr.responseType = options.responseType || 'json';

    if (options.xhr) {
        if (options.xhr.requestHeaders) {
            // add custom request headers
            options.xhr.requestHeaders.forEach(header => {
                xhr.setRequestHeader(header.key, header.value);
            });
        }
        if (options.xhr.withCredentials) {
            // use credentials
            xhr.withCredentials = true;
        }
    }

    xhr.addEventListener('progress', e => {
        instance.fireEvent('progress', e);
        if (e.lengthComputable && e.loaded == e.total) {
            fired100 = true;
        }
    });
    xhr.addEventListener('load', e => {
        if (!fired100) {
            instance.fireEvent('progress', e);
        }
        instance.fireEvent('load', e);
        if (200 == xhr.status || 206 == xhr.status) {
            instance.fireEvent('success', xhr.response, e);
        } else {
            instance.fireEvent('error', e);
        }
    });
    xhr.addEventListener('error', e => instance.fireEvent('error', e));
    xhr.send();
    instance.xhr = xhr;
    return instance;
}