eslint/docs/src/rules/object-shorthand.md

   1 ---
   2 title: object-shorthand
   3 layout: doc
   4 rule_type: suggestion
   5 related_rules:
   6 - no-useless-rename
   7 further_reading:
   8 - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer
   9 ---
  10
  11
  12
  13 ECMAScript 6 provides a concise form for defining object literal methods and properties. This
  14 syntax can make defining complex object literals much cleaner.
  15
  16 Here are a few common examples using the ES5 syntax:
  17
  18 ```js
  19 // properties
  20 var foo = {
  21     x: x,
  22     y: y,
  23     z: z,
  24 };
  25
  26 // methods
  27 var foo = {
  28     a: function() {},
  29     b: function() {}
  30 };
  31 ```
  32
  33 Now here are ES6 equivalents:
  34
  35 ```js
  36 /*eslint-env es6*/
  37
  38 // properties
  39 var foo = {x, y, z};
  40
  41 // methods
  42 var foo = {
  43     a() {},
  44     b() {}
  45 };
  46 ```
  47
  48 ## Rule Details
  49
  50 This rule enforces the use of the shorthand syntax. This applies
  51 to all methods (including generators) defined in object literals and any
  52 properties defined where the key name matches name of the assigned variable.
  53
  54 Each of the following properties would warn:
  55
  56 ```js
  57 /*eslint object-shorthand: "error"*/
  58 /*eslint-env es6*/
  59
  60 var foo = {
  61     w: function() {},
  62     x: function *() {},
  63     [y]: function() {},
  64     z: z
  65 };
  66 ```
  67
  68 In that case the expected syntax would have been:
  69
  70 ```js
  71 /*eslint object-shorthand: "error"*/
  72 /*eslint-env es6*/
  73
  74 var foo = {
  75     w() {},
  76     *x() {},
  77     [y]() {},
  78     z
  79 };
  80 ```
  81
  82 This rule does not flag arrow functions inside of object literals.
  83 The following will *not* warn:
  84
  85 ```js
  86 /*eslint object-shorthand: "error"*/
  87 /*eslint-env es6*/
  88
  89 var foo = {
  90     x: (y) => y
  91 };
  92 ```
  93
  94 ## Options
  95
  96 The rule takes an option which specifies when it should be applied. It can be set to one of the following values:
  97
  98 * `"always"` (default) expects that the shorthand will be used whenever possible.
  99 * `"methods"` ensures the method shorthand is used (also applies to generators).
 100 * `"properties"` ensures the property shorthand is used (where the key and variable name match).
 101 * `"never"` ensures that no property or method shorthand is used in any object literal.
 102 * `"consistent"` ensures that either all shorthand or all long-form will be used in an object literal.
 103 * `"consistent-as-needed"` ensures that either all shorthand or all long-form will be used in an object literal, but ensures all shorthand whenever possible.
 104
 105 You can set the option in configuration like this:
 106
 107 ```json
 108 {
 109     "object-shorthand": ["error", "always"]
 110 }
 111 ```
 112
 113 Additionally, the rule takes an optional object configuration:
 114
 115 * `"avoidQuotes": true` indicates that long-form syntax is preferred whenever the object key is a string literal (default: `false`). Note that this option can only be enabled when the string option is set to `"always"`, `"methods"`, or `"properties"`.
 116 * `"ignoreConstructors": true` can be used to prevent the rule from reporting errors for constructor functions. (By default, the rule treats constructors the same way as other functions.) Note that this option can only be enabled when the string option is set to `"always"` or `"methods"`.
 117 * `"methodsIgnorePattern"` (`string`) for methods whose names match this regex pattern, the method shorthand will not be enforced. Note that this option can only be used when the string option is set to `"always"` or `"methods"`.
 118 * `"avoidExplicitReturnArrows": true` indicates that methods are preferred over explicit-return arrow functions for function properties. (By default, the rule allows either of these.) Note that this option can only be enabled when the string option is set to `"always"` or `"methods"`.
 119
 120 ### `avoidQuotes`
 121
 122 ```json
 123 {
 124     "object-shorthand": ["error", "always", { "avoidQuotes": true }]
 125 }
 126 ```
 127
 128 Example of **incorrect** code for this rule with the `"always", { "avoidQuotes": true }` option:
 129
 130 ::: incorrect
 131
 132 ```js
 133 /*eslint object-shorthand: ["error", "always", { "avoidQuotes": true }]*/
 134 /*eslint-env es6*/
 135
 136 var foo = {
 137     "bar-baz"() {}
 138 };
 139 ```
 140
 141 :::
 142
 143 Example of **correct** code for this rule with the `"always", { "avoidQuotes": true }` option:
 144
 145 ::: correct
 146
 147 ```js
 148 /*eslint object-shorthand: ["error", "always", { "avoidQuotes": true }]*/
 149 /*eslint-env es6*/
 150
 151 var foo = {
 152     "bar-baz": function() {},
 153     "qux": qux
 154 };
 155 ```
 156
 157 :::
 158
 159 ### `ignoreConstructors`
 160
 161 ```json
 162 {
 163     "object-shorthand": ["error", "always", { "ignoreConstructors": true }]
 164 }
 165 ```
 166
 167 Example of **correct** code for this rule with the `"always", { "ignoreConstructors": true }` option:
 168
 169 ::: correct
 170
 171 ```js
 172 /*eslint object-shorthand: ["error", "always", { "ignoreConstructors": true }]*/
 173 /*eslint-env es6*/
 174
 175 var foo = {
 176     ConstructorFunction: function() {}
 177 };
 178 ```
 179
 180 :::
 181
 182 ### `methodsIgnorePattern`
 183
 184 Example of **correct** code for this rule with the `"always", { "methodsIgnorePattern": "^bar$" }` option:
 185
 186 ::: correct
 187
 188 ```js
 189 /*eslint object-shorthand: ["error", "always", { "methodsIgnorePattern": "^bar$" }]*/
 190
 191 var foo = {
 192     bar: function() {}
 193 };
 194 ```
 195
 196 :::
 197
 198 ### `avoidExplicitReturnArrows`
 199
 200 ```json
 201 {
 202     "object-shorthand": ["error", "always", { "avoidExplicitReturnArrows": true }]
 203 }
 204 ```
 205
 206 Example of **incorrect** code for this rule with the `"always", { "avoidExplicitReturnArrows": true }` option:
 207
 208 ::: incorrect
 209
 210 ```js
 211 /*eslint object-shorthand: ["error", "always", { "avoidExplicitReturnArrows": true }]*/
 212 /*eslint-env es6*/
 213
 214 var foo = {
 215   foo: (bar, baz) => {
 216     return bar + baz;
 217   },
 218
 219   qux: (foobar) => {
 220     return foobar * 2;
 221   }
 222 };
 223 ```
 224
 225 :::
 226
 227 Example of **correct** code for this rule with the `"always", { "avoidExplicitReturnArrows": true }` option:
 228
 229 ::: correct
 230
 231 ```js
 232 /*eslint object-shorthand: ["error", "always", { "avoidExplicitReturnArrows": true }]*/
 233 /*eslint-env es6*/
 234
 235 var foo = {
 236   foo(bar, baz) {
 237     return bar + baz;
 238   },
 239
 240   qux: foobar => foobar * 2
 241 };
 242 ```
 243
 244 :::
 245
 246 Example of **incorrect** code for this rule with the `"consistent"` option:
 247
 248 ::: incorrect
 249
 250 ```js
 251 /*eslint object-shorthand: [2, "consistent"]*/
 252 /*eslint-env es6*/
 253
 254 var foo = {
 255     a,
 256     b: "foo",
 257 };
 258 ```
 259
 260 :::
 261
 262 Examples of **correct** code for this rule with the `"consistent"` option:
 263
 264 ::: correct
 265
 266 ```js
 267 /*eslint object-shorthand: [2, "consistent"]*/
 268 /*eslint-env es6*/
 269
 270 var foo = {
 271     a: a,
 272     b: "foo"
 273 };
 274
 275 var bar = {
 276     a,
 277     b,
 278 };
 279 ```
 280
 281 :::
 282
 283 Example of **incorrect** code with the `"consistent-as-needed"` option, which is very similar to `"consistent"`:
 284
 285 ::: incorrect
 286
 287 ```js
 288 /*eslint object-shorthand: [2, "consistent-as-needed"]*/
 289 /*eslint-env es6*/
 290
 291 var foo = {
 292     a: a,
 293     b: b,
 294 };
 295 ```
 296
 297 :::
 298
 299 ## When Not To Use It
 300
 301 Anyone not yet in an ES6 environment would not want to apply this rule. Others may find the terseness of the shorthand
 302 syntax harder to read and may not want to encourage it with this rule.