Add timeout/interval methods to WebhookClient (fixes discordjs#1181),…

… and clean up docs (discordjs#1204)

* fix up 1181

* Clean up documentation

* Update WebhookClient.js

src/client/WebhookClient.js

@@ -10,13 +10,13 @@ const Util = require('../util/Util');
  */
 class WebhookClient extends Webhook {
   /**
-   * @param {string} id The id of the webhook.
-   * @param {string} token the token of the webhook.
+   * @param {string} id ID of the webhook
+   * @param {string} token Token of the webhook
    * @param {ClientOptions} [options] Options for the client
    * @example
    * // create a new webhook and send a message
-   * let hook = new Discord.WebhookClient('1234', 'abcdef')
-   * hook.sendMessage('This will send a message').catch(console.error)
+   * const hook = new Discord.WebhookClient('1234', 'abcdef');
+   * hook.sendMessage('This will send a message').catch(console.error);
    */
   constructor(id, token, options) {
     super(null, id, token);
@@ -35,11 +35,83 @@ class WebhookClient extends Webhook {
     this.rest = new RESTManager(this);
 
     /**
-     * The Data Resolver of the Client
+     * The data resolver of the client
      * @type {ClientDataResolver}
      * @private
      */
     this.resolver = new ClientDataResolver(this);
+
+    /**
+     * Timeouts set by {@link WebhookClient#setTimeout} that are still active
+     * @type {Set<Timeout>}
+     * @private
+     */
+    this._timeouts = new Set();
+
+    /**
+     * Intervals set by {@link WebhookClient#setInterval} that are still active
+     * @type {Set<Timeout>}
+     * @private
+     */
+    this._intervals = new Set();
+  }
+
+  /**
+   * Sets a timeout that will be automatically cancelled if the client is destroyed.
+   * @param {Function} fn Function to execute
+   * @param {number} delay Time to wait before executing (in milliseconds)
+   * @param {...*} args Arguments for the function
+   * @returns {Timeout}
+   */
+  setTimeout(fn, delay, ...args) {
+    const timeout = setTimeout(() => {
+      fn();
+      this._timeouts.delete(timeout);
+    }, delay, ...args);
+    this._timeouts.add(timeout);
+    return timeout;
+  }
+
+  /**
+   * Clears a timeout.
+   * @param {Timeout} timeout Timeout to cancel
+   */
+  clearTimeout(timeout) {
+    clearTimeout(timeout);
+    this._timeouts.delete(timeout);
+  }
+
+  /**
+   * Sets an interval that will be automatically cancelled if the client is destroyed.
+   * @param {Function} fn Function to execute
+   * @param {number} delay Time to wait before executing (in milliseconds)
+   * @param {...*} args Arguments for the function
+   * @returns {Timeout}
+   */
+  setInterval(fn, delay, ...args) {
+    const interval = setInterval(fn, delay, ...args);
+    this._intervals.add(interval);
+    return interval;
+  }
+
+  /**
+   * Clears an interval.
+   * @param {Timeout} interval Interval to cancel
+   */
+  clearInterval(interval) {
+    clearInterval(interval);
+    this._intervals.delete(interval);
+  }
+
+
+  /**
+   * Destroys the client.
+   */
+  destroy() {
+    for (const t of this._timeouts) clearTimeout(t);
+    for (const i of this._intervals) clearInterval(i);
+    this._timeouts.clear();
+    this._intervals.clear();
   }
 }