useValidTypeof

JavaScript (and super languages)

Summary

• Rule available since: v1.0.0
• Diagnostic Category: lint/correctness/useValidTypeof
• This rule is recommended, which means is enabled by default.
• This rule has an unsafe fix.
• The default severity of this rule is error.
• Sources:
  • Same as valid-typeof

How to configure

biome.json

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

Description

This rule checks that the result of a typeof expression is compared to a valid value.

Examples

Invalid

typeof foo === "strnig";

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

  ✖ “strnig” is not a valid typeof value.
  
  > 1 │ typeof foo === “strnig”;
      │                ^^^^^^^^
    2 │ 
  

typeof foo == "undefimed";

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

  ✖ “undefimed” is not a valid typeof value.
  
  > 1 │ typeof foo == “undefimed”;
      │               ^^^^^^^^^^^
    2 │ 
  

typeof bar != "nunber";

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

  ✖ “nunber” is not a valid typeof value.
  
  > 1 │ typeof bar != “nunber”;
      │               ^^^^^^^^
    2 │ 
  

typeof foo === undefined;

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

  ✖ Invalid typeof comparison.
  
  > 1 │ typeof foo === undefined;
      │                ^^^^^^^^^
    2 │ 
  
  ℹ Compare with one of the following string literals:
  
  - “bigint”
  - “boolean”
  - “function”
  - “number”
  - “object”
  - “string”
  - “symbol”
  - “undefined”
  

typeof foo == 0;

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

  ✖ Invalid typeof comparison.
  
  > 1 │ typeof foo == 0;
      │               ^
    2 │ 
  
  ℹ Compare with one of the following string literals:
  
  - “bigint”
  - “boolean”
  - “function”
  - “number”
  - “object”
  - “string”
  - “symbol”
  - “undefined”
  

Valid

typeof foo === "string";

typeof bar == "undefined";

typeof bar === typeof qux;

typeof foo === bar

Related links

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• Rule options
• Source Code
• Test Cases