source: frontend/node_modules/events/tests/modify-in-emit.js

// Copyright Joyent, Inc. and other Node contributors.
//
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// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
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// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
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// USE OR OTHER DEALINGS IN THE SOFTWARE.

require('./common');
var assert = require('assert');
var events = require('../');

var callbacks_called = [];

var e = new events.EventEmitter();

function callback1() {
  callbacks_called.push('callback1');
  e.on('foo', callback2);
  e.on('foo', callback3);
  e.removeListener('foo', callback1);
}

function callback2() {
  callbacks_called.push('callback2');
  e.removeListener('foo', callback2);
}

function callback3() {
  callbacks_called.push('callback3');
  e.removeListener('foo', callback3);
}

e.on('foo', callback1);
assert.strictEqual(e.listeners('foo').length, 1);

e.emit('foo');
assert.strictEqual(e.listeners('foo').length, 2);
assert.ok(Array.isArray(callbacks_called));
assert.strictEqual(callbacks_called.length, 1);
assert.strictEqual(callbacks_called[0], 'callback1');

e.emit('foo');
assert.strictEqual(e.listeners('foo').length, 0);
assert.ok(Array.isArray(callbacks_called));
assert.strictEqual(callbacks_called.length, 3);
assert.strictEqual(callbacks_called[0], 'callback1');
assert.strictEqual(callbacks_called[1], 'callback2');
assert.strictEqual(callbacks_called[2], 'callback3');

e.emit('foo');
assert.strictEqual(e.listeners('foo').length, 0);
assert.ok(Array.isArray(callbacks_called));
assert.strictEqual(callbacks_called.length, 3);
assert.strictEqual(callbacks_called[0], 'callback1');
assert.strictEqual(callbacks_called[1], 'callback2');
assert.strictEqual(callbacks_called[2], 'callback3');

e.on('foo', callback1);
e.on('foo', callback2);
assert.strictEqual(e.listeners('foo').length, 2);
e.removeAllListeners('foo');
assert.strictEqual(e.listeners('foo').length, 0);

// Verify that removing callbacks while in emit allows emits to propagate to
// all listeners
callbacks_called = [];

e.on('foo', callback2);
e.on('foo', callback3);
assert.strictEqual(2, e.listeners('foo').length);
e.emit('foo');
assert.ok(Array.isArray(callbacks_called));
assert.strictEqual(callbacks_called.length, 2);
assert.strictEqual(callbacks_called[0], 'callback2');
assert.strictEqual(callbacks_called[1], 'callback3');
assert.strictEqual(0, e.listeners('foo').length);