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0e7d57af35
A handful of modules (including readable-streams) make inappropriate use of the internal _events property. One such use is to prepend an event listener to the front of the array of listeners. This adds EE.prototype.prependListener() and EE.prototype.prependOnceListener() methods to add handlers to the *front* of the listener array. Doc update and test case is included. Fixes: https://github.com/nodejs/node/issues/1817 PR-URL: https://github.com/nodejs/node/pull/6032 Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com> Reviewed-By: Brian White <mscdex@mscdex.net>
42 lines
940 B
JavaScript
42 lines
940 B
JavaScript
'use strict';
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const common = require('../common');
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const EventEmitter = require('events');
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const assert = require('assert');
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const myEE = new EventEmitter();
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var m = 0;
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// This one comes last.
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myEE.on('foo', common.mustCall(() => assert.equal(m, 2)));
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// This one comes second.
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myEE.prependListener('foo', common.mustCall(() => assert.equal(m++, 1)));
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// This one comes first.
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myEE.prependOnceListener('foo', common.mustCall(() => assert.equal(m++, 0)));
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myEE.emit('foo');
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// Test fallback if prependListener is undefined.
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const stream = require('stream');
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const util = require('util');
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delete EventEmitter.prototype.prependListener;
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function Writable() {
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this.writable = true;
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stream.Stream.call(this);
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}
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util.inherits(Writable, stream.Stream);
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function Readable() {
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this.readable = true;
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stream.Stream.call(this);
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}
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util.inherits(Readable, stream.Stream);
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const w = new Writable();
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const r = new Readable();
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r.pipe(w);
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