events_test.js
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// Licensed to the Software Freedom Conservancy (SFC) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The SFC licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
'use strict';
const EventEmitter = require('../../lib/events').EventEmitter;
const assert = require('assert');
const sinon = require('sinon');
describe('EventEmitter', function() {
describe('#emit()', function() {
it('can emit events when nothing is registered', function() {
let emitter = new EventEmitter;
emitter.emit('foo');
// Ok if no errors are thrown.
});
it('can pass args to listeners on emit', function() {
let emitter = new EventEmitter;
let now = Date.now();
let messages = [];
emitter.on('foo', (arg) => messages.push(arg));
emitter.emit('foo', now);
assert.deepEqual([now], messages);
emitter.emit('foo', now + 15);
assert.deepEqual([now, now + 15], messages);
});
});
describe('#addListener()', function() {
it('can add multiple listeners for one event', function() {
let emitter = new EventEmitter;
let count = 0;
emitter.addListener('foo', () => count++);
emitter.addListener('foo', () => count++);
emitter.addListener('foo', () => count++);
emitter.emit('foo');
assert.equal(3, count);
});
it('only registers each listener function once', function() {
let emitter = new EventEmitter;
let count = 0;
let onFoo = () => count++;
emitter.addListener('foo', onFoo);
emitter.addListener('foo', onFoo);
emitter.addListener('foo', onFoo);
emitter.emit('foo');
assert.equal(1, count);
emitter.emit('foo');
assert.equal(2, count);
});
it('allows users to specify a custom scope', function() {
let obj = {
count: 0,
inc: function() {
this.count++;
}
};
let emitter = new EventEmitter;
emitter.addListener('foo', obj.inc, obj);
emitter.emit('foo');
assert.equal(1, obj.count);
emitter.emit('foo');
assert.equal(2, obj.count);
});
});
describe('#once()', function() {
it('only calls registered callback once', function() {
let emitter = new EventEmitter;
let count = 0;
emitter.once('foo', () => count++);
emitter.once('foo', () => count++);
emitter.once('foo', () => count++);
emitter.emit('foo');
assert.equal(3, count);
emitter.emit('foo');
assert.equal(3, count);
emitter.emit('foo');
assert.equal(3, count);
});
});
describe('#removeListeners()', function() {
it('only removes the given listener function', function() {
let emitter = new EventEmitter;
let count = 0;
emitter.addListener('foo', () => count++);
emitter.addListener('foo', () => count++);
let toRemove = () => count++;
emitter.addListener('foo', toRemove);
emitter.emit('foo');
assert.equal(3, count);
emitter.removeListener('foo', toRemove);
emitter.emit('foo');
assert.equal(5, count);
});
});
describe('#removeAllListeners()', function() {
it('only removes listeners for type if specified', function() {
let emitter = new EventEmitter;
let count = 0;
emitter.addListener('foo', () => count++);
emitter.addListener('foo', () => count++);
emitter.addListener('foo', () => count++);
emitter.addListener('bar', () => count++);
emitter.emit('foo');
assert.equal(3, count);
emitter.removeAllListeners('foo');
emitter.emit('foo');
assert.equal(3, count);
emitter.emit('bar');
assert.equal(4, count);
});
it('removes absolutely all listeners if no type specified', function() {
let emitter = new EventEmitter;
let count = 0;
emitter.addListener('foo', () => count++);
emitter.addListener('bar', () => count++);
emitter.addListener('baz', () => count++);
emitter.addListener('baz', () => count++);
emitter.emit('foo');
assert.equal(1, count);
emitter.emit('baz');
assert.equal(3, count);
emitter.removeAllListeners();
emitter.emit('foo');
assert.equal(3, count);
emitter.emit('bar');
assert.equal(3, count);
emitter.emit('baz');
assert.equal(3, count);
});
});
});