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51 lines
1.5 KiB
JavaScript
51 lines
1.5 KiB
JavaScript
/**
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* Copyright 2013 Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* @providesModule emptyFunction
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*/
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var copyProperties = require("./copyProperties");
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function makeEmptyFunction(arg) {
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return function() {
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return arg;
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};
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}
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/**
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* This function accepts and discards inputs; it has no side effects. This is
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* primarily useful idiomatically for overridable function endpoints which
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* always need to be callable, since JS lacks a null-call idiom ala Cocoa.
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*/
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function emptyFunction() {}
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copyProperties(emptyFunction, {
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thatReturns: makeEmptyFunction,
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thatReturnsFalse: makeEmptyFunction(false),
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thatReturnsTrue: makeEmptyFunction(true),
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thatReturnsNull: makeEmptyFunction(null),
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thatReturnsThis: function() { return this; },
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thatReturnsArgument: function(arg) { return arg; },
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mustImplement: function(module, property) {
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return function() {
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if (true) {
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throw new Error(module + '.' + property + ' must be implemented!');
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}
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};
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}
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});
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module.exports = emptyFunction;
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