README.md
1 # is-descriptor [](https://www.npmjs.com/package/is-descriptor) [](https://npmjs.org/package/is-descriptor) [](https://npmjs.org/package/is-descriptor) [](https://travis-ci.org/jonschlinkert/is-descriptor) 2 3 > Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for data descriptors and accessor descriptors. 4 5 ## Install 6 7 Install with [npm](https://www.npmjs.com/): 8 9 ```sh 10 $ npm install --save is-descriptor 11 ``` 12 13 ## Usage 14 15 ```js 16 var isDescriptor = require('is-descriptor'); 17 18 isDescriptor({value: 'foo'}) 19 //=> true 20 isDescriptor({get: function(){}, set: function(){}}) 21 //=> true 22 isDescriptor({get: 'foo', set: function(){}}) 23 //=> false 24 ``` 25 26 You may also check for a descriptor by passing an object as the first argument and property name (`string`) as the second argument. 27 28 ```js 29 var obj = {}; 30 obj.foo = 'abc'; 31 32 Object.defineProperty(obj, 'bar', { 33 value: 'xyz' 34 }); 35 36 isDescriptor(obj, 'foo'); 37 //=> true 38 isDescriptor(obj, 'bar'); 39 //=> true 40 ``` 41 42 ## Examples 43 44 ### value type 45 46 `false` when not an object 47 48 ```js 49 isDescriptor('a'); 50 //=> false 51 isDescriptor(null); 52 //=> false 53 isDescriptor([]); 54 //=> false 55 ``` 56 57 ### data descriptor 58 59 `true` when the object has valid properties with valid values. 60 61 ```js 62 isDescriptor({value: 'foo'}); 63 //=> true 64 isDescriptor({value: noop}); 65 //=> true 66 ``` 67 68 `false` when the object has invalid properties 69 70 ```js 71 isDescriptor({value: 'foo', bar: 'baz'}); 72 //=> false 73 isDescriptor({value: 'foo', bar: 'baz'}); 74 //=> false 75 isDescriptor({value: 'foo', get: noop}); 76 //=> false 77 isDescriptor({get: noop, value: noop}); 78 //=> false 79 ``` 80 81 `false` when a value is not the correct type 82 83 ```js 84 isDescriptor({value: 'foo', enumerable: 'foo'}); 85 //=> false 86 isDescriptor({value: 'foo', configurable: 'foo'}); 87 //=> false 88 isDescriptor({value: 'foo', writable: 'foo'}); 89 //=> false 90 ``` 91 92 ### accessor descriptor 93 94 `true` when the object has valid properties with valid values. 95 96 ```js 97 isDescriptor({get: noop, set: noop}); 98 //=> true 99 isDescriptor({get: noop}); 100 //=> true 101 isDescriptor({set: noop}); 102 //=> true 103 ``` 104 105 `false` when the object has invalid properties 106 107 ```js 108 isDescriptor({get: noop, set: noop, bar: 'baz'}); 109 //=> false 110 isDescriptor({get: noop, writable: true}); 111 //=> false 112 isDescriptor({get: noop, value: true}); 113 //=> false 114 ``` 115 116 `false` when an accessor is not a function 117 118 ```js 119 isDescriptor({get: noop, set: 'baz'}); 120 //=> false 121 isDescriptor({get: 'foo', set: noop}); 122 //=> false 123 isDescriptor({get: 'foo', bar: 'baz'}); 124 //=> false 125 isDescriptor({get: 'foo', set: 'baz'}); 126 //=> false 127 ``` 128 129 `false` when a value is not the correct type 130 131 ```js 132 isDescriptor({get: noop, set: noop, enumerable: 'foo'}); 133 //=> false 134 isDescriptor({set: noop, configurable: 'foo'}); 135 //=> false 136 isDescriptor({get: noop, configurable: 'foo'}); 137 //=> false 138 ``` 139 140 ## About 141 142 ### Related projects 143 144 * [is-accessor-descriptor](https://www.npmjs.com/package/is-accessor-descriptor): Returns true if a value has the characteristics of a valid JavaScript accessor descriptor. | [homepage](https://github.com/jonschlinkert/is-accessor-descriptor "Returns true if a value has the characteristics of a valid JavaScript accessor descriptor.") 145 * [is-data-descriptor](https://www.npmjs.com/package/is-data-descriptor): Returns true if a value has the characteristics of a valid JavaScript data descriptor. | [homepage](https://github.com/jonschlinkert/is-data-descriptor "Returns true if a value has the characteristics of a valid JavaScript data descriptor.") 146 * [is-descriptor](https://www.npmjs.com/package/is-descriptor): Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for… [more](https://github.com/jonschlinkert/is-descriptor) | [homepage](https://github.com/jonschlinkert/is-descriptor "Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for data descriptors and accessor descriptors.") 147 * [isobject](https://www.npmjs.com/package/isobject): Returns true if the value is an object and not an array or null. | [homepage](https://github.com/jonschlinkert/isobject "Returns true if the value is an object and not an array or null.") 148 149 ### Contributing 150 151 Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new). 152 153 ### Contributors 154 155 | **Commits** | **Contributor** | 156 | --- | --- | 157 | 24 | [jonschlinkert](https://github.com/jonschlinkert) | 158 | 1 | [doowb](https://github.com/doowb) | 159 | 1 | [wtgtybhertgeghgtwtg](https://github.com/wtgtybhertgeghgtwtg) | 160 161 ### Building docs 162 163 _(This project's readme.md is generated by [verb](https://github.com/verbose/verb-generate-readme), please don't edit the readme directly. Any changes to the readme must be made in the [.verb.md](.verb.md) readme template.)_ 164 165 To generate the readme, run the following command: 166 167 ```sh 168 $ npm install -g verbose/verb#dev verb-generate-readme && verb 169 ``` 170 171 ### Running tests 172 173 Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command: 174 175 ```sh 176 $ npm install && npm test 177 ``` 178 179 ### Author 180 181 **Jon Schlinkert** 182 183 * [github/jonschlinkert](https://github.com/jonschlinkert) 184 * [twitter/jonschlinkert](https://twitter.com/jonschlinkert) 185 186 ### License 187 188 Copyright © 2017, [Jon Schlinkert](https://github.com/jonschlinkert). 189 Released under the [MIT License](LICENSE). 190 191 *** 192 193 _This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.6.0, on July 22, 2017._