isEmpty.js 2.1 KB
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import getTag from './getTag.js'
import isArguments from './isArguments.js'
import isArrayLike from './isArrayLike.js'
import isBuffer from './isBuffer.js'
import isPrototype from './isPrototype.js'
import isTypedArray from './isTypedArray.js'

/** Used to check objects for own properties. */
const hasOwnProperty = Object.prototype.hasOwnProperty

/**
 * Checks if `value` is an empty object, collection, map, or set.
 * 检查' value '是否为空对象、集合、映射或集合。
 * Objects are considered empty if they have no own enumerable string keyed
 * properties.
 * 如果对象没有自己的可枚举字符串作为键,则认为它们是空的
 * 属性。
 * Array-like values such as `arguments` objects, arrays, buffers, strings, or
 * jQuery-like collections are considered empty if they have a `length` of `0`.
 * Similarly, maps and sets are considered empty if they have a `size` of `0`.
 * 类似数组的值,如‘arguments’对象、数组、缓冲区、字符串或
 * 类似于jquery的集合如果“长度”为“0”,就会被认为是空的。
 * 类似地,如果映射和集合的“size”为“0”,则认为它们是空的。
 * @since 0.1.0
 * @category Lang
 * @param {*} value 要检查的值。
 * @returns {boolean} 如果' value '为空,则返回' true ',否则返回' false '。
 * @example
 *
 * isEmpty(null)
 * // => true
 *
 * isEmpty(true)
 * // => true
 *
 * isEmpty(1)
 * // => true
 *
 * isEmpty([1, 2, 3])
 * // => false
 *
 * isEmpty('abc')
 * // => false
 *
 * isEmpty({ 'a': 1 })
 * // => false
 */
function isEmpty(value) {
  if (value == null) {
    return true
  }
  if (isArrayLike(value) &&
      (Array.isArray(value) || typeof value === 'string' || typeof value.splice === 'function' ||
        isBuffer(value) || isTypedArray(value) || isArguments(value))) {
    return !value.length
  }
  const tag = getTag(value)
  if (tag == '[object Map]' || tag == '[object Set]') {
    return !value.size
  }
  if (isPrototype(value)) {
    return !Object.keys(value).length
  }
  for (const key in value) {
    if (hasOwnProperty.call(value, key)) {
      return false
    }
  }
  return true
}

export default isEmpty