57 lines
1.9 KiB
JavaScript
57 lines
1.9 KiB
JavaScript
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/**
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* Add an event listener bound to the context of the superClass.
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*
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* @param {HTMLElement} node Element to attach the event listener to.
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* @param {String} eventName Name of the event.
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* @param {String} cbName Name of the handler.
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*/
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export const EventHelpers = function(superClass) {
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return class extends superClass {
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listen(node, eventName, cbName) {
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this.__boundEventListeners = this.__boundEventListeners || new WeakMap();
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const boundListener = this[cbName].bind(this);
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const eventKey = `${eventName}_${cbName}`;
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let listeners = this.__boundEventListeners.get(node);
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// If there is already a handler for the event assigned we stop here.
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if (listeners && typeof listeners[eventKey] === 'function') return;
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if (!listeners) {
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listeners = {};
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}
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listeners[eventKey] = boundListener;
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this.__boundEventListeners.set(node, listeners);
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node.addEventListener(eventName, boundListener);
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}
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/**
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* Remove an event listener bound to the context of the superClass.
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*
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* @param {HTMLElement} node Element to attach the event listener to.
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* @param {String} eventName Name of the event.
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* @param {String} cbName Name of the handler.
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*/
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unlisten(node, eventName, cbName) {
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this.__boundEventListeners = this.__boundEventListeners || new WeakMap();
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const listeners = this.__boundEventListeners.get(node);
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const eventKey = `${eventName}_${cbName}`;
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if (listeners && typeof listeners[eventKey]) {
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node.removeEventListener(eventName, listeners[eventKey]);
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listeners[eventKey] = null;
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}
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}
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once(node, eventName, cbName) {
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const wrappedCbName = `__onceCb__${cbName}`;
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this[wrappedCbName] = (...args) => {
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this[cbName](...args);
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this.unlisten(node, eventName, wrappedCbName);
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};
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this.listen(node, eventName, wrappedCbName);
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}
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}
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}
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