92 lines
2.2 KiB
JavaScript
92 lines
2.2 KiB
JavaScript
const ajax = (function() { "use strict";
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class NetworkError extends Error {}
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class UnexpectedMimeError extends Error {}
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class InvalidJsonError extends Error {}
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const MIME_JSON = "application/json";
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/**
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* Wrap a function so that it receives `this` as first argument.
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*/
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function thisToArg(f) {
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return function(...rest) {
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return f(this, ...rest);
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}
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}
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function xhrInitForPromise(resolve, reject, url, method, headers) {
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const t_resolve = thisToArg(resolve),
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t_reject = thisToArg(reject);
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let xhr = new XMLHttpRequest();
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xhr.addEventListener("load", t_resolve);
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xhr.addEventListener("error", t_resolve);
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xhr.addEventListener("abort", t_reject);
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xhr.addEventListener("timeout", t_reject);
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xhr.open(method, url);
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for (let header of Object.getOwnPropertyNames(headers)) {
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xhr.setRequestHeader(header, headers[header]);
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}
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return xhr;
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}
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function xhrParseJsonResponse(xhr) {
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if (xhr.status == 0) {
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console.error(xhr);
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throw new NetworkError("Failed to connect to server");
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}
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if (!xhr.responseText) {
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const json = null;
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} else {
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const contentType = xhr.getResponseHeader("Content-Type");
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if (contentType != MIME_JSON) {
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throw new UnexpectedMimeError(`Server did not reply with JSON but with ${contentType}`);
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}
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try {
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const json = JSON.parse(xhr.responseText);
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} catch(e) {
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throw new InvalidJsonError();
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}
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}
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return {
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ok: 200 <= xhr.status && xhr.status < 300,
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status: xhr.status,
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statusText: xhr.statusText,
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getHeader: xhr.getResponseHeader,
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json,
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xhr,
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};
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}
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function getJson(url, options={}) {
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if (!options.headers) options.headers = {};
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options.headers["Accept"] = MIME_JSON;
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return new Promise((resolve, reject) => {
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let xhr = xhrInitForPromise(resolve, reject, url, "GET", options.headers);
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xhr.send();
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}).then(xhrParseJsonResponse);
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}
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function postJson(url, data={}, options={}) {
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if (!options.headers) options.headers = {};
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options.headers["Content-Type"] = MIME_JSON;
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options.headers["Accept"] = MIME_JSON;
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return new Promise((resolve, reject) => {
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let xhr = xhrInitForPromise(resolve, reject, url, "POST", options.headers);
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xhr.send(JSON.stringify(data));
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}).then(xhrParseJsonResponse);
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}
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return {
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NetworkError, UnexpectedMimeError, InvalidJsonError,
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getJson, postJson
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};
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})();
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