_.includes(collection, value, [fromIndex=0])

78

_.includes(collection, value, [fromIndex=0])

_.includes检查value是否出现在collection中,如果collection是字符串,就检查value是否是子串,否则使用SameValueZero规则检测是否相等。如果fromIndex是负数,就作为从结尾开始的偏移

参数

collection (Array|Object|string): 需要查找判断的集合
value (*): 查找的值
[fromIndex=0] (number): 查找的其实索引

返回值

(boolean): 如果找到了value返回true,否则false

例子

_.includes([1, 2, 3], 1);
// => true
 
_.includes([1, 2, 3], 1, 2);
// => false
 
_.includes({ 'a': 1, 'b': 2 }, 1);
// => true
 
_.includes('abcd', 'bc');
// => true

源代码:

/**
 * lodash (Custom Build) <https://lodash.com/>
 * Build: `lodash modularize exports="npm" -o ./`
 * Copyright jQuery Foundation and other contributors <https://jquery.org/>
 * Released under MIT license <https://lodash.com/license>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 */

/** Used as references for various `Number` constants. */
var INFINITY = 1 / 0,
    MAX_SAFE_INTEGER = 9007199254740991,
    MAX_INTEGER = 1.7976931348623157e+308,
    NAN = 0 / 0;

/** `Object#toString` result references. */
var argsTag = '[object Arguments]',
    funcTag = '[object Function]',
    genTag = '[object GeneratorFunction]',
    stringTag = '[object String]',
    symbolTag = '[object Symbol]';

/** Used to match leading and trailing whitespace. */
var reTrim = /^\s+|\s+$/g;

/** Used to detect bad signed hexadecimal string values. */
var reIsBadHex = /^[-+]0x[0-9a-f]+$/i;

/** Used to detect binary string values. */
var reIsBinary = /^0b[01]+$/i;

/** Used to detect octal string values. */
var reIsOctal = /^0o[0-7]+$/i;

/** Used to detect unsigned integer values. */
var reIsUint = /^(?:0|[1-9]\d*)$/;

/** Built-in method references without a dependency on `root`. */
var freeParseInt = parseInt;

/**
 * A specialized version of `_.map` for arrays without support for iteratee
 * shorthands.
 *
 * @private
 * @param {Array} [array] The array to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @returns {Array} Returns the new mapped array.
 */
//类似原生数组方法map
function arrayMap(array, iteratee) {
  var index = -1,//循环索引
      length = array ? array.length : 0,//数组长度
      result = Array(length);//结果数组

  while (++index < length) {//循环数组,结果数组的元素是每一个元素调用iteratee返回的结果
    result[index] = iteratee(array[index], index, array);
  }
  return result;
}

/**
 * The base implementation of `_.findIndex` and `_.findLastIndex` without
 * support for iteratee shorthands.
 *
 * @private
 * @param {Array} array The array to inspect.
 * @param {Function} predicate The function invoked per iteration.
 * @param {number} fromIndex The index to search from.
 * @param {boolean} [fromRight] Specify iterating from right to left.
 * @returns {number} Returns the index of the matched value, else `-1`.
 */
//_.findIndex和_.findLastIndex的基础实现
function baseFindIndex(array, predicate, fromIndex, fromRight) {
  var length = array.length,//数组长度
      index = fromIndex + (fromRight ? 1 : -1);//其实索引处理

  while ((fromRight ? index-- : ++index < length)) {
    //循环判断每个元素调用predicate后的返回值,如果找到就返回索引
    if (predicate(array[index], index, array)) {
      return index;
    }
  }
  return -1;//找不到返回-1
}

/**
 * The base implementation of `_.indexOf` without `fromIndex` bounds checks.
 *
 * @private
 * @param {Array} array The array to inspect.
 * @param {*} value The value to search for.
 * @param {number} fromIndex The index to search from.
 * @returns {number} Returns the index of the matched value, else `-1`.
 */
//_.indexOf的基础实现
function baseIndexOf(array, value, fromIndex) {
  if (value !== value) {//如果value是NaN,就调用baseFindIndex查找array中NaN的索引
    return baseFindIndex(array, baseIsNaN, fromIndex);
  }
  var index = fromIndex - 1,//循环索引
      length = array.length;//数组长度

  while (++index < length) {//循环遍历用严格等于判断,如果找到就返回索引
    if (array[index] === value) {
      return index;
    }
  }
  return -1;//找不到返回-1
}

/**
 * The base implementation of `_.isNaN` without support for number objects.
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is `NaN`, else `false`.
 */
function baseIsNaN(value) {
  return value !== value;
}

/**
 * The base implementation of `_.times` without support for iteratee shorthands
 * or max array length checks.
 *
 * @private
 * @param {number} n The number of times to invoke `iteratee`.
 * @param {Function} iteratee The function invoked per iteration.
 * @returns {Array} Returns the array of results.
 */
//_.times的基础实现,循环n次,返回iteratee处理的index组成的数组
function baseTimes(n, iteratee) {
  var index = -1,//循环索引
      result = Array(n);//结果数组,长度为n

  while (++index < n) {//循环n次,结果数组每一个元素是当前index被iteratee处理后的结果
    result[index] = iteratee(index);
  }
  return result;
}

/**
 * The base implementation of `_.values` and `_.valuesIn` which creates an
 * array of `object` property values corresponding to the property names
 * of `props`.
 *
 * @private
 * @param {Object} object The object to query.
 * @param {Array} props The property names to get values for.
 * @returns {Object} Returns the array of property values.
 */
//_.values和_.valuesIn的基础实现,创建object的属性值组成的数组,属性值对应的属性名数组是props参数
function baseValues(object, props) {
  return arrayMap(props, function(key) {
    return object[key];//循环props属性名数组,创建出属性值组成的数组
  });
}

/**
 * Creates a unary function that invokes `func` with its argument transformed.
 *
 * @private
 * @param {Function} func The function to wrap.
 * @param {Function} transform The argument transform.
 * @returns {Function} Returns the new function.
 */
function overArg(func, transform) {
  return function(arg) {
    return func(transform(arg));
  };
}

/** Used for built-in method references. */
var objectProto = Object.prototype;

/** Used to check objects for own properties. */
var hasOwnProperty = objectProto.hasOwnProperty;

/**
 * Used to resolve the
 * [`toStringTag`](http://ecma-international.org/ecma-262/7.0/#sec-object.prototype.tostring)
 * of values.
 */
var objectToString = objectProto.toString;

/** Built-in value references. */
var propertyIsEnumerable = objectProto.propertyIsEnumerable;

/* Built-in method references for those with the same name as other `lodash` methods. */
var nativeKeys = overArg(Object.keys, Object),
    nativeMax = Math.max;

/**
 * Creates an array of the enumerable property names of the array-like `value`.
 *
 * @private
 * @param {*} value The value to query.
 * @param {boolean} inherited Specify returning inherited property names.
 * @returns {Array} Returns the array of property names.
 */
//创建一个array-like对象的可枚举的属性名组成的数组
//inherited布尔值,是否指定需要返回继承来的属性
function arrayLikeKeys(value, inherited) {
  // Safari 8.1 makes `arguments.callee` enumerable in strict mode.
  // Safari 9 makes `arguments.length` enumerable in strict mode.
  var result = (isArray(value) || isArguments(value))
    ? baseTimes(value.length, String)
    : [];
    //结果数组初始化,如果value是数组或者arguments对象,使用baseTimes处理,baseTimes返回的数组的元素是索引的字符串值组成的数组,否则为空数组
  var length = result.length,//结果数组长度
      skipIndexes = !!length;//是否需要跳过数字索引

  for (var key in value) {
    if ((inherited || hasOwnProperty.call(value, key)) &&
        !(skipIndexes && (key == 'length' || isIndex(key, length)))) {
      //如果需要返回继承来的属性值,或者当前key是value自身属性
      //并且判断是否是不是length属性或者数字索引属性,因为这两种属性需要跳过
      result.push(key);
    }
  }
  return result;
}

/**
 * The base implementation of `_.keys` which doesn't treat sparse arrays as dense.
 *
 * @private
 * @param {Object} object The object to query.
 * @returns {Array} Returns the array of property names.
 */
//_.keys的基础实现,类似于Object.keys()
function baseKeys(object) {
  if (!isPrototype(object)) {//如果object不是一个prototype对象,用nativekeys处理,也就是原生的Object.keys
    return nativeKeys(object);
  }
  var result = [];//结果数组
  for (var key in Object(object)) {//遍历object的属性
    if (hasOwnProperty.call(object, key) && key != 'constructor') {
      //如果当前key是object自身属性,并且不是构造函数,就插入结果数组
      result.push(key);
    }
  }
  return result;
}

/**
 * Checks if `value` is a valid array-like index.
 *
 * @private
 * @param {*} value The value to check.
 * @param {number} [length=MAX_SAFE_INTEGER] The upper bounds of a valid index.
 * @returns {boolean} Returns `true` if `value` is a valid index, else `false`.
 */
//判断一个值是否是一个有效的array-like对象的索引
function isIndex(value, length) {
  length = length == null ? MAX_SAFE_INTEGER : length;
  return !!length &&
    (typeof value == 'number' || reIsUint.test(value)) &&
    (value > -1 && value % 1 == 0 && value < length);
}

/**
 * Checks if `value` is likely a prototype object.
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a prototype, else `false`.
 */
//判断一个值是否类似一个prototype对象
function isPrototype(value) {
  var Ctor = value && value.constructor,
      proto = (typeof Ctor == 'function' && Ctor.prototype) || objectProto;

  return value === proto;
}

/**
 * Checks if `value` is in `collection`. If `collection` is a string, it's
 * checked for a substring of `value`, otherwise
 * [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
 * is used for equality comparisons. If `fromIndex` is negative, it's used as
 * the offset from the end of `collection`.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Collection
 * @param {Array|Object|string} collection The collection to inspect.
 * @param {*} value The value to search for.
 * @param {number} [fromIndex=0] The index to search from.
 * @param- {Object} [guard] Enables use as an iteratee for methods like `_.reduce`.
 * @returns {boolean} Returns `true` if `value` is found, else `false`.
 * @example
 *
 * _.includes([1, 2, 3], 1);
 * // => true
 *
 * _.includes([1, 2, 3], 1, 2);
 * // => false
 *
 * _.includes({ 'a': 1, 'b': 2 }, 1);
 * // => true
 *
 * _.includes('abcd', 'bc');
 * // => true
 */
//检查value是否出现在collection中,如果collection是字符串,就检查value是否是子串,否则使用SameValueZero规则检测是否相等。如果fromIndex是负数,就作为从结尾开始的偏移
function includes(collection, value, fromIndex, guard) {
  collection = isArrayLike(collection) ? collection : values(collection);
  //如果collection是array-like对象,不做处理,否则调用values获取collection的自身可枚举属性值组成的数组
  fromIndex = (fromIndex && !guard) ? toInteger(fromIndex) : 0;
  //如果传递了fromIndex查询的其实索引,就将其转换成整数

  var length = collection.length;//集合的长度
  if (fromIndex < 0) {//如果起始索引是负数,就做处理,负数起始索引作为从结尾往前的偏移量
    fromIndex = nativeMax(length + fromIndex, 0);
  }
  return isString(collection)
    ? (fromIndex <= length && collection.indexOf(value, fromIndex) > -1)
    : (!!length && baseIndexOf(collection, value, fromIndex) > -1);
    //如果collection是字符串。如果起始索引小于字符串长度,就使用indexOf查询是否value是集合的子串
    //如果collection不是字符串。如果有长度,就调用baseIndexOf查询是否包含value
}

/**
 * Checks if `value` is likely an `arguments` object.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is an `arguments` object,
 *  else `false`.
 * @example
 *
 * _.isArguments(function() { return arguments; }());
 * // => true
 *
 * _.isArguments([1, 2, 3]);
 * // => false
 */
//判断一个值是否是一个arguments对象
function isArguments(value) {
  // Safari 8.1 makes `arguments.callee` enumerable in strict mode.
  return isArrayLikeObject(value) && hasOwnProperty.call(value, 'callee') &&
    (!propertyIsEnumerable.call(value, 'callee') || objectToString.call(value) == argsTag);
}

/**
 * Checks if `value` is classified as an `Array` object.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is an array, else `false`.
 * @example
 *
 * _.isArray([1, 2, 3]);
 * // => true
 *
 * _.isArray(document.body.children);
 * // => false
 *
 * _.isArray('abc');
 * // => false
 *
 * _.isArray(_.noop);
 * // => false
 */
//判断一个值是否是数组
var isArray = Array.isArray;

/**
 * Checks if `value` is array-like. A value is considered array-like if it's
 * not a function and has a `value.length` that's an integer greater than or
 * equal to `0` and less than or equal to `Number.MAX_SAFE_INTEGER`.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is array-like, else `false`.
 * @example
 *
 * _.isArrayLike([1, 2, 3]);
 * // => true
 *
 * _.isArrayLike(document.body.children);
 * // => true
 *
 * _.isArrayLike('abc');
 * // => true
 *
 * _.isArrayLike(_.noop);
 * // => false
 */
//判断一个值是否是array-like对象
function isArrayLike(value) {
  return value != null && isLength(value.length) && !isFunction(value);
}

/**
 * This method is like `_.isArrayLike` except that it also checks if `value`
 * is an object.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is an array-like object,
 *  else `false`.
 * @example
 *
 * _.isArrayLikeObject([1, 2, 3]);
 * // => true
 *
 * _.isArrayLikeObject(document.body.children);
 * // => true
 *
 * _.isArrayLikeObject('abc');
 * // => false
 *
 * _.isArrayLikeObject(_.noop);
 * // => false
 */
//判断一个值是否是一个array-like对象并且也是一个object-like对象
function isArrayLikeObject(value) {
  return isObjectLike(value) && isArrayLike(value);
}

/**
 * Checks if `value` is classified as a `Function` object.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a function, else `false`.
 * @example
 *
 * _.isFunction(_);
 * // => true
 *
 * _.isFunction(/abc/);
 * // => false
 */
//判断一个值是否是function对象
function isFunction(value) {
  // The use of `Object#toString` avoids issues with the `typeof` operator
  // in Safari 8-9 which returns 'object' for typed array and other constructors.
  var tag = isObject(value) ? objectToString.call(value) : '';
  return tag == funcTag || tag == genTag;
}

/**
 * Checks if `value` is a valid array-like length.
 *
 * **Note:** This method is loosely based on
 * [`ToLength`](http://ecma-international.org/ecma-262/7.0/#sec-tolength).
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a valid length, else `false`.
 * @example
 *
 * _.isLength(3);
 * // => true
 *
 * _.isLength(Number.MIN_VALUE);
 * // => false
 *
 * _.isLength(Infinity);
 * // => false
 *
 * _.isLength('3');
 * // => false
 */
//判断一个值是否是有效的array-like对象的length属性
function isLength(value) {
  return typeof value == 'number' &&
    value > -1 && value % 1 == 0 && value <= MAX_SAFE_INTEGER;
}

/**
 * Checks if `value` is the
 * [language type](http://www.ecma-international.org/ecma-262/7.0/#sec-ecmascript-language-types)
 * of `Object`. (e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`)
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is an object, else `false`.
 * @example
 *
 * _.isObject({});
 * // => true
 *
 * _.isObject([1, 2, 3]);
 * // => true
 *
 * _.isObject(_.noop);
 * // => true
 *
 * _.isObject(null);
 * // => false
 */
//判断一个值是否是一个对象
function isObject(value) {
  var type = typeof value;
  return !!value && (type == 'object' || type == 'function');
}

/**
 * Checks if `value` is object-like. A value is object-like if it's not `null`
 * and has a `typeof` result of "object".
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is object-like, else `false`.
 * @example
 *
 * _.isObjectLike({});
 * // => true
 *
 * _.isObjectLike([1, 2, 3]);
 * // => true
 *
 * _.isObjectLike(_.noop);
 * // => false
 *
 * _.isObjectLike(null);
 * // => false
 */
//判断一个值是否是一个object-like对象
function isObjectLike(value) {
  return !!value && typeof value == 'object';
}

/**
 * Checks if `value` is classified as a `String` primitive or object.
 *
 * @static
 * @since 0.1.0
 * @memberOf _
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a string, else `false`.
 * @example
 *
 * _.isString('abc');
 * // => true
 *
 * _.isString(1);
 * // => false
 */
//判断一个值是否是原生字符串或者字符串对象
function isString(value) {
  return typeof value == 'string' ||
    (!isArray(value) && isObjectLike(value) && objectToString.call(value) == stringTag);
}

/**
 * Checks if `value` is classified as a `Symbol` primitive or object.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a symbol, else `false`.
 * @example
 *
 * _.isSymbol(Symbol.iterator);
 * // => true
 *
 * _.isSymbol('abc');
 * // => false
 */
//判断一个值是否是原生的Symbol类型
function isSymbol(value) {
  return typeof value == 'symbol' ||
    (isObjectLike(value) && objectToString.call(value) == symbolTag);
}

/**
 * Converts `value` to a finite number.
 *
 * @static
 * @memberOf _
 * @since 4.12.0
 * @category Lang
 * @param {*} value The value to convert.
 * @returns {number} Returns the converted number.
 * @example
 *
 * _.toFinite(3.2);
 * // => 3.2
 *
 * _.toFinite(Number.MIN_VALUE);
 * // => 5e-324
 *
 * _.toFinite(Infinity);
 * // => 1.7976931348623157e+308
 *
 * _.toFinite('3.2');
 * // => 3.2
 */
//将一个值转换成 有限 的数字
function toFinite(value) {
  if (!value) {//如果value为假,返回0
    return value === 0 ? value : 0;
  }
  value = toNumber(value);//将value转换成number类型
  if (value === INFINITY || value === -INFINITY) {//如果是无限
    var sign = (value < 0 ? -1 : 1);//正负标记
    return sign * MAX_INTEGER;//转换成有限值
  }
  return value === value ? value : 0;//返回结果,如果是NaN就返回0
}

/**
 * Converts `value` to an integer.
 *
 * **Note:** This method is loosely based on
 * [`ToInteger`](http://www.ecma-international.org/ecma-262/7.0/#sec-tointeger).
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to convert.
 * @returns {number} Returns the converted integer.
 * @example
 *
 * _.toInteger(3.2);
 * // => 3
 *
 * _.toInteger(Number.MIN_VALUE);
 * // => 0
 *
 * _.toInteger(Infinity);
 * // => 1.7976931348623157e+308
 *
 * _.toInteger('3.2');
 * // => 3
 */
//将一个值转换成整数
function toInteger(value) {
  var result = toFinite(value),//将value转换成有限值
      remainder = result % 1;//取余获取到小数部分

  return result === result ? (remainder ? result - remainder : result) : 0;
  //如果是NaN返回0,如果是小数,减去小数部分,如果没有小数部分直接返回
}

/**
 * Converts `value` to a number.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to process.
 * @returns {number} Returns the number.
 * @example
 *
 * _.toNumber(3.2);
 * // => 3.2
 *
 * _.toNumber(Number.MIN_VALUE);
 * // => 5e-324
 *
 * _.toNumber(Infinity);
 * // => Infinity
 *
 * _.toNumber('3.2');
 * // => 3.2
 */
//将一个值转换成数字
function toNumber(value) {
  if (typeof value == 'number') {//如果是number直接返回
    return value;
  }
  if (isSymbol(value)) {//如果是Symbol类型,返回NaN
    return NAN;
  }
  if (isObject(value)) {//如果value是对象
    var other = typeof value.valueOf == 'function' ? value.valueOf() : value;
    //如果value有valueOf属性,就调用valueOf()取值,否则取原值
    value = isObject(other) ? (other + '') : other;
    //如果other是对象,就转成字符串,否则取原值
  }
  if (typeof value != 'string') {//value被转成字符串后的处理
    return value === 0 ? value : +value;
  }
  value = value.replace(reTrim, '');//正则把空白字符都转换成空字符串
  var isBinary = reIsBinary.test(value);//判断是否是二进制
  return (isBinary || reIsOctal.test(value))
    ? freeParseInt(value.slice(2), isBinary ? 2 : 8)
    : (reIsBadHex.test(value) ? NAN : +value);
    //如果是二进制或者八进制,调用parseInt转换
    //否则判断不良签名的十六进制转为NaN
}

/**
 * Creates an array of the own enumerable property names of `object`.
 *
 * **Note:** Non-object values are coerced to objects. See the
 * [ES spec](http://ecma-international.org/ecma-262/7.0/#sec-object.keys)
 * for more details.
 *
 * @static
 * @since 0.1.0
 * @memberOf _
 * @category Object
 * @param {Object} object The object to query.
 * @returns {Array} Returns the array of property names.
 * @example
 *
 * function Foo() {
 *   this.a = 1;
 *   this.b = 2;
 * }
 *
 * Foo.prototype.c = 3;
 *
 * _.keys(new Foo);
 * // => ['a', 'b'] (iteration order is not guaranteed)
 *
 * _.keys('hi');
 * // => ['0', '1']
 */
//创建对象的自身可枚举属性名组成的数组
function keys(object) {
  return isArrayLike(object) ? arrayLikeKeys(object) : baseKeys(object);
  //如果是array-like对象,调用arrayLikeKeys获取对象的key组成数组,否则调用baseKeys
}

/**
 * Creates an array of the own enumerable string keyed property values of `object`.
 *
 * **Note:** Non-object values are coerced to objects.
 *
 * @static
 * @since 0.1.0
 * @memberOf _
 * @category Object
 * @param {Object} object The object to query.
 * @returns {Array} Returns the array of property values.
 * @example
 *
 * function Foo() {
 *   this.a = 1;
 *   this.b = 2;
 * }
 *
 * Foo.prototype.c = 3;
 *
 * _.values(new Foo);
 * // => [1, 2] (iteration order is not guaranteed)
 *
 * _.values('hi');
 * // => ['h', 'i']
 */
//创建对象的自身可枚举的字符串属性key对应的属性值组成的数组
function values(object) {
  return object ? baseValues(object, keys(object)) : [];
  //object存在就调用baseValues生成object对象的属性值组成的数组,否则返回空数组
}

module.exports = includes;

 

posted @ 2018-11-07 10:30  hahazexia  阅读(390)  评论(0)    收藏  举报