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node_modules/events/tests/prepend.js

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+'use strict';
+
+var common = require('./common');
+var EventEmitter = require('../');
+var assert = require('assert');
+
+var myEE = new EventEmitter();
+var m = 0;
+// This one comes last.
+myEE.on('foo', common.mustCall(function () {
+  assert.strictEqual(m, 2);
+}));
+
+// This one comes second.
+myEE.prependListener('foo', common.mustCall(function () {
+  assert.strictEqual(m++, 1);
+}));
+
+// This one comes first.
+myEE.prependOnceListener('foo',
+                         common.mustCall(function () {
+                           assert.strictEqual(m++, 0);
+                         }));
+
+myEE.emit('foo');
+
+// Verify that the listener must be a function
+assert.throws(function () {
+  var ee = new EventEmitter();
+  ee.prependOnceListener('foo', null);
+}, 'TypeError: The "listener" argument must be of type Function. Received type object');