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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs.

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/*
 * Copyright 2017 The Closure Compiler Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @fileoverview RefasterJS templates for replacing the usage of
 * Array.prototype.indexOf to determine whether an element is in the array or
 * not with Array.prototype.includes.
 *
 * Note that Array.prototype.includes handles NaN in a different way:
 * [1, 2, NaN].includes(NaN); // true
 * [1, 2, NaN].indexOf(NaN); // -1
 *
 * Available in:
 * - Chrome 47+
 * - Firefox 43+
 * - Edge 14+
 * - Opera 34+
 * - Safari 9+
 * - IE n/a
 *
 * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes
 *
 * This refactoring covers the most common cases in which this can be expressed:
 *
 * 'arr.includes(elem)' is equivalent to:
 * - arr.indexOf(elem) != -1
 * - arr.indexOf(elem) !== -1
 * - arr.indexOf(elem) > -1
 * - arr.indexOf(elem) >= 0
 *
 * '!arr.includes(elem)' is equivalent to:
 * - arr.indexOf(elem) == -1
 * - arr.indexOf(elem) === -1
 * - arr.indexOf(elem) < 0
 */

// elem found in the array.

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function before_indexOfNotEqualsMinusOne(arr, elem) {
  arr.indexOf(elem) != -1;
}

/**
 * @param {!Array} arr
 * @param {*} elem
 */
function after_indexOfNotEqualsMinusOne(arr, elem) {
  arr.includes(elem);
}

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function before_indexOfStronglyNotEqualsMinusOne(arr, elem) {
  arr.indexOf(elem) !== -1;
}

/**
 * @param {!Array} arr
 * @param {*} elem
 */
function after_indexOfStronglyNotEqualsMinusOne(arr, elem) {
  arr.includes(elem);
}

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function before_indexOfGreaterThanMinusOne(arr, elem) {
  arr.indexOf(elem) > -1;
}

/**
 * @param {!Array} arr
 * @param {*} elem
 */
function after_indexOfGreaterThanMinusOne(arr, elem) {
  arr.includes(elem);
}

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function before_indexOfGreaterThanOrEqualsZero(arr, elem) {
  arr.indexOf(elem) >= 0;
}

/**
 * @param {!Array} arr
 * @param {*} elem
 */
function after_indexOfGreaterThanOrEqualsZero(arr, elem) {
  arr.includes(elem);
}

// elem NOT found in the array.

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function before_indexOfEqualsMinusOne(arr, elem) {
  arr.indexOf(elem) == -1;
}

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function after_indexOfEqualsMinusOne(arr, elem) {
  !arr.includes(elem);
}

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function before_indexOfStronglyEqualsMinusOne(arr, elem) {
  arr.indexOf(elem) === -1;
}

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function after_indexOfStronglyEqualsMinusOne(arr, elem) {
  !arr.includes(elem);
}

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function before_indexOfLessThanZero(arr, elem) {
  arr.indexOf(elem) < 0;
}

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function after_indexOfLessThanZero(arr, elem) {
  !arr.includes(elem);
}

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function before_bitwiseNot(arr, elem) {
  ~arr.indexOf(elem);
}

/**
 * @param {!Array} arr
 * @param {*} elem
 * @suppress {uselessCode}
 */
function after_bitwiseNot(arr, elem) {
  arr.includes(elem);
}