eslint/docs/src/rules/no-import-assign.md

   1 ---
   2 title: no-import-assign
   3 layout: doc
   4 rule_type: problem
   5 ---
   6
   7
   8
   9 The updates of imported bindings by ES Modules cause runtime errors.
  10
  11 ## Rule Details
  12
  13 This rule warns the assignments, increments, and decrements of imported bindings.
  14
  15 Examples of **incorrect** code for this rule:
  16
  17 ::: incorrect
  18
  19 ```js
  20 /*eslint no-import-assign: "error"*/
  21
  22 import mod, { named } from "./mod.mjs"
  23 import * as mod_ns from "./mod.mjs"
  24
  25 mod = 1          // ERROR: 'mod' is readonly.
  26 named = 2        // ERROR: 'named' is readonly.
  27 mod_ns.named = 3 // ERROR: The members of 'mod_ns' are readonly.
  28 mod_ns = {}      // ERROR: 'mod_ns' is readonly.
  29 // Can't extend 'mod_ns'
  30 Object.assign(mod_ns, { foo: "foo" }) // ERROR: The members of 'mod_ns' are readonly.
  31 ```
  32
  33 :::
  34
  35 Examples of **correct** code for this rule:
  36
  37 ::: correct
  38
  39 ```js
  40 /*eslint no-import-assign: "error"*/
  41
  42 import mod, { named } from "./mod.mjs"
  43 import * as mod_ns from "./mod.mjs"
  44
  45 mod.prop = 1
  46 named.prop = 2
  47 mod_ns.named.prop = 3
  48
  49 // Known Limitation
  50 function test(obj) {
  51     obj.named = 4 // Not errored because 'obj' is not namespace objects.
  52 }
  53 test(mod_ns) // Not errored because it doesn't know that 'test' updates the member of the argument.
  54 ```
  55
  56 :::
  57
  58 ## When Not To Use It
  59
  60 If you don't want to be notified about modifying imported bindings, you can disable this rule.