useValidTypeof

Diagnostic Category: lint/suspicious/useValidTypeof

JavaScript (and super languages)

Since: v1.0.0

Sources:

Same as: valid-typeof

Description

This rule verifies the result of typeof $expr unary expressions is being compared to valid values, either string literals containing valid type names or other typeof expressions

Examples

Invalid

typeof foo === "strnig"

code-block.js:1:16 lint/suspicious/useValidTypeof ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Invalid typeof comparison value
  
  > 1 │ typeof foo === “strnig”
      │                ^^^^^^^^
    2 │ 
  
  ℹ not a valid type name

typeof foo == "undefimed"

code-block.js:1:15 lint/suspicious/useValidTypeof ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Invalid typeof comparison value
  
  > 1 │ typeof foo == “undefimed”
      │               ^^^^^^^^^^^
    2 │ 
  
  ℹ not a valid type name

typeof bar != "nunber"

code-block.js:1:15 lint/suspicious/useValidTypeof ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Invalid typeof comparison value
  
  > 1 │ typeof bar != “nunber”
      │               ^^^^^^^^
    2 │ 
  
  ℹ not a valid type name

typeof bar !== "fucntion"

code-block.js:1:16 lint/suspicious/useValidTypeof ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Invalid typeof comparison value
  
  > 1 │ typeof bar !== “fucntion”
      │                ^^^^^^^^^^
    2 │ 
  
  ℹ not a valid type name

typeof foo === undefined

code-block.js:1:16 lint/suspicious/useValidTypeof  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Invalid typeof comparison value
  
  > 1 │ typeof foo === undefined
      │                ^^^^^^^^^
    2 │ 
  
  ℹ not a string literal
  
  ℹ Unsafe fix: Compare the result of typeof with a valid type name
  
    1 │ typeof·foo·===·“undefined”
      │                +         +

typeof bar == Object

code-block.js:1:15 lint/suspicious/useValidTypeof  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Invalid typeof comparison value
  
  > 1 │ typeof bar == Object
      │               ^^^^^^
    2 │ 
  
  ℹ not a string literal
  
  ℹ Unsafe fix: Compare the result of typeof with a valid type name
  
    1   │ - typeof·bar·==·Object
      1 │ + typeof·bar·==·“object”
    2 2 │

typeof foo === baz

code-block.js:1:16 lint/suspicious/useValidTypeof ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Invalid typeof comparison value
  
  > 1 │ typeof foo === baz
      │                ^^^
    2 │ 
  
  ℹ not a string literal

typeof foo == 5

code-block.js:1:15 lint/suspicious/useValidTypeof ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Invalid typeof comparison value
  
  > 1 │ typeof foo == 5
      │               ^
    2 │ 
  
  ℹ not a string literal

typeof foo == -5

code-block.js:1:15 lint/suspicious/useValidTypeof ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Invalid typeof comparison value
  
  > 1 │ typeof foo == -5
      │               ^^
    2 │ 
  
  ℹ not a string literal

Valid

typeof foo === "string"

typeof bar == "undefined"

typeof bar === typeof qux

How to configure

{
  "linter": {
    "rules": {
      "suspicious": {
        "useValidTypeof": "error"
      }
    }
  }
}