84 lines
1.8 KiB
JavaScript
84 lines
1.8 KiB
JavaScript
const _ = require('underscore');
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/*
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* Periodically fetches a model/collection. It waits for ongoing
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* fetch requests before trying to fetch again. A stop condition
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* can be specified.
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*
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* Usage example:
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*
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* var poller = new Poller(model, {
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* interval: 1000,
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* stopWhen: function (model) {
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* return model.get('state') === 'completed';
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* }
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* });
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*
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* poller.start();
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*
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* // ...
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*
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* poller.stop();
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*
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*/
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const Poller = function (model, options) {
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this.model = model;
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this.numberOfRequests = 0;
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this.polling = false;
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this.interval = options['interval'];
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if (typeof this.interval !== 'function') {
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this.interval = function () { return options['interval']; };
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}
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this.stopWhen = options['stopWhen'];
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this.error = options['error'];
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this.autoStart = options['autoStart'];
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if (this.autoStart) {
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this.start();
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}
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};
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Poller.prototype.start = function () {
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if (this.timeout) {
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return;
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}
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this._scheduleFetch();
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};
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Poller.prototype._scheduleFetch = function () {
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this.timeout = setTimeout(this._fetch.bind(this), this.interval(this.numberOfRequests));
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};
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Poller.prototype._fetch = function () {
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if (!this.polling) {
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this.polling = true;
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this.model.fetch({
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success: () => {
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this.polling = false;
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this.numberOfRequests++;
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if (this._continuePolling()) {
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this._scheduleFetch();
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}
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},
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error: (e) => {
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_.isFunction(this.error) && this.error(this.model);
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}
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});
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}
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};
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Poller.prototype._continuePolling = function () {
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return !this.stopWhen ||
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(_.isFunction(this.stopWhen) && !this.stopWhen(this.model));
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};
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Poller.prototype.stop = function () {
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this.polling = false;
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clearTimeout(this.timeout);
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delete this.timeout;
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};
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module.exports = Poller;
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