69 lines
1.4 KiB
JavaScript
69 lines
1.4 KiB
JavaScript
export default class EventEmitter {
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constructor() {
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this._handlersByName = {};
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}
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emit(name, value) {
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const handlers = this._handlersByName[name];
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if (handlers) {
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for(const h of handlers) {
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h(value);
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}
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}
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}
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on(name, callback) {
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let handlers = this._handlersByName[name];
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if (!handlers) {
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this._handlersByName[name] = handlers = new Set();
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}
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handlers.add(callback);
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}
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off(name, callback) {
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const handlers = this._handlersByName[name];
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if (handlers) {
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handlers.delete(callback);
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if (handlers.length === 0) {
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delete this._handlersByName[name];
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}
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}
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}
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}
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//#ifdef TESTS
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export function tests() {
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return {
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test_on_off(assert) {
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let counter = 0;
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const e = new EventEmitter();
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const callback = () => counter += 1;
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e.on("change", callback);
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e.emit("change");
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e.off("change", callback);
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e.emit("change");
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assert.equal(counter, 1);
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},
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test_emit_value(assert) {
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let value = 0;
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const e = new EventEmitter();
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const callback = (v) => value = v;
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e.on("change", callback);
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e.emit("change", 5);
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e.off("change", callback);
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assert.equal(value, 5);
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},
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test_double_on(assert) {
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let counter = 0;
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const e = new EventEmitter();
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const callback = () => counter += 1;
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e.on("change", callback);
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e.on("change", callback);
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e.emit("change");
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e.off("change", callback);
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assert.equal(counter, 1);
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}
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};
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}
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//#endif
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