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'use strict';
const common = require('../common');
const assert = require('assert');
const EventEmitter = require('events');
const e = new EventEmitter();
e.once('hello', common.mustCall(function(a, b) {}));
e.emit('hello', 'a', 'b');
e.emit('hello', 'a', 'b');
e.emit('hello', 'a', 'b');
e.emit('hello', 'a', 'b');
const remove = function() {
common.fail('once->foo should not be emitted');
};
e.once('foo', remove);
e.removeListener('foo', remove);
e.emit('foo');
e.once('e', common.mustCall(function() {
e.emit('e');
}));
e.once('e', common.mustCall(function() {}));
e.emit('e');
// Verify that the listener must be a function
assert.throws(() => {
const ee = new EventEmitter();
ee.once('foo', null);
}, /^TypeError: "listener" argument must be a function$/);
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