mirror of
https://github.com/whoisclebs/lodash.git
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104 lines
3.0 KiB
JavaScript
104 lines
3.0 KiB
JavaScript
/** Used to detect unsigned integer values. */
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/** Used to detect unsigned integer values. */
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var reIsUint = /^\d+$/;
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/**
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* Used as the [maximum length](http://ecma-international.org/ecma-262/6.0/#sec-number.max_safe_integer)
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* of an array-like value.
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*/
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var MAX_SAFE_INTEGER = 9007199254740991;
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/**
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* The base implementation of `_.at` without support for string collections
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* and individual key arguments.
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*
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* @private
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* @param {Array|Object} collection The collection to iterate over.
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* @param {number[]|string[]} props The property names or indexes of elements to pick.
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* @returns {Array} Returns the new array of picked elements.
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*/
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function baseAt(collection, props) {
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var index = -1,
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isNil = collection == null,
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isArr = !isNil && isArrayLike(collection),
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length = isArr ? collection.length : 0,
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propsLength = props.length,
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result = Array(propsLength);
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while(++index < propsLength) {
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var key = props[index];
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if (isArr) {
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result[index] = isIndex(key, length) ? collection[key] : undefined;
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} else {
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result[index] = isNil ? undefined : collection[key];
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}
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}
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return result;
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}
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/**
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* The base implementation of `_.property` without support for deep paths.
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*
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* @private
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* @param {string} key The key of the property to get.
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* @returns {Function} Returns the new function.
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*/
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function baseProperty(key) {
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return function(object) {
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return object == null ? undefined : object[key];
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};
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}
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/**
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* Gets the "length" property value of `object`.
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*
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* **Note:** This function is used to avoid a [JIT bug](https://bugs.webkit.org/show_bug.cgi?id=142792)
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* that affects Safari on at least iOS 8.1-8.3 ARM64.
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*
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* @private
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* @param {Object} object The object to query.
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* @returns {*} Returns the "length" value.
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*/
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var getLength = baseProperty('length');
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/**
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* Checks if `value` is array-like.
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*
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* @private
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* @param {*} value The value to check.
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* @returns {boolean} Returns `true` if `value` is array-like, else `false`.
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*/
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function isArrayLike(value) {
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return value != null && isLength(getLength(value));
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}
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/**
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* Checks if `value` is a valid array-like index.
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*
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* @private
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* @param {*} value The value to check.
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* @param {number} [length=MAX_SAFE_INTEGER] The upper bounds of a valid index.
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* @returns {boolean} Returns `true` if `value` is a valid index, else `false`.
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*/
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function isIndex(value, length) {
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value = (typeof value == 'number' || reIsUint.test(value)) ? +value : -1;
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length = length == null ? MAX_SAFE_INTEGER : length;
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return value > -1 && value % 1 == 0 && value < length;
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}
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/**
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* Checks if `value` is a valid array-like length.
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*
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* **Note:** This function is based on [`ToLength`](http://ecma-international.org/ecma-262/6.0/#sec-tolength).
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*
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* @private
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* @param {*} value The value to check.
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* @returns {boolean} Returns `true` if `value` is a valid length, else `false`.
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*/
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function isLength(value) {
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return typeof value == 'number' && value > -1 && value % 1 == 0 && value <= MAX_SAFE_INTEGER;
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}
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module.exports = baseAt;
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