eslint/docs/rules/no-restricted-globals.md

   1 # Disallow specific global variables (no-restricted-globals)
   2
   3 Disallowing usage of specific global variables can be useful if you want to allow a set of global
   4 variables by enabling an environment, but still want to disallow some of those.
   5
   6 For instance, early Internet Explorer versions exposed the current DOM event as a global variable
   7 `event`, but using this variable has been considered as a bad practice for a long time. Restricting
   8 this will make sure this variable isn't used in browser code.
   9
  10 ## Rule Details
  11
  12 This rule allows you to specify global variable names that you don't want to use in your application.
  13
  14 ## Options
  15
  16 This rule takes a list of strings, where each string is a global to be restricted:
  17
  18 ```json
  19 {
  20     "rules": {
  21         "no-restricted-globals": ["error", "event", "fdescribe"]
  22     }
  23 }
  24 ```
  25
  26 Alternatively, the rule also accepts objects, where the global name and an optional custom message are specified:
  27
  28 ```json
  29 {
  30     "rules": {
  31         "no-restricted-globals": [
  32             "error",
  33             {
  34                 "name": "event",
  35                 "message": "Use local parameter instead."
  36             },
  37             {
  38                 "name": "fdescribe",
  39                 "message": "Do not commit fdescribe. Use describe instead."
  40             }
  41         ]
  42     }
  43 }
  44 ```
  45
  46 Examples of **incorrect** code for sample `"event", "fdescribe"` global variable names:
  47
  48 ```js
  49 /*global event, fdescribe*/
  50 /*eslint no-restricted-globals: ["error", "event", "fdescribe"]*/
  51
  52 function onClick() {
  53     console.log(event);
  54 }
  55
  56 fdescribe("foo", function() {
  57 });
  58 ```
  59
  60 Examples of **correct** code for a sample `"event"` global variable name:
  61
  62 ```js
  63 /*global event*/
  64 /*eslint no-restricted-globals: ["error", "event"]*/
  65
  66 import event from "event-module";
  67 ```
  68
  69 ```js
  70 /*global event*/
  71 /*eslint no-restricted-globals: ["error", "event"]*/
  72
  73 var event = 1;
  74 ```
  75
  76 Examples of **incorrect** code for a sample `"event"` global variable name, along with a custom error message:
  77
  78 ```js
  79 /*global event*/
  80 /* eslint no-restricted-globals: ["error", { name: "event", message: "Use local parameter instead." }] */
  81
  82 function onClick() {
  83     console.log(event);    // Unexpected global variable 'event'. Use local parameter instead.
  84 }
  85 ```
  86
  87 ## Related Rules
  88
  89 * [no-restricted-properties](no-restricted-properties.md)
  90 * [no-restricted-syntax](no-restricted-syntax.md)