useValidTypeof

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"

warning[useValidTypeof]: Invalid `typeof` comparison value
  ┌─ useValidTypeof.js:1:16
  │
1 │ typeof foo === "strnig"
  │                -------- not a valid type name

typeof foo == "undefimed"

warning[useValidTypeof]: Invalid `typeof` comparison value
  ┌─ useValidTypeof.js:1:15
  │
1 │ typeof foo == "undefimed"
  │               ----------- not a valid type name

typeof bar != "nunber"

warning[useValidTypeof]: Invalid `typeof` comparison value
  ┌─ useValidTypeof.js:1:15
  │
1 │ typeof bar != "nunber"
  │               -------- not a valid type name

typeof bar !== "fucntion"

warning[useValidTypeof]: Invalid `typeof` comparison value
  ┌─ useValidTypeof.js:1:16
  │
1 │ typeof bar !== "fucntion"
  │                ---------- not a valid type name

typeof foo === undefined

warning[useValidTypeof]: Invalid `typeof` comparison value
  ┌─ useValidTypeof.js:1:16
  │
1 │ typeof foo === undefined
  │                --------- not a string literal

Suggested fix: Compare the result of `typeof` with a valid type name
    | @@ -1 +1 @@
0   | - typeof foo === undefined
  0 | + typeof foo === "undefined"

typeof bar == Object

warning[useValidTypeof]: Invalid `typeof` comparison value
  ┌─ useValidTypeof.js:1:15
  │
1 │ typeof bar == Object
  │               ------ not a string literal

Suggested fix: Compare the result of `typeof` with a valid type name
    | @@ -1 +1 @@
0   | - typeof bar == Object
  0 | + typeof bar == "object"

typeof foo === baz

warning[useValidTypeof]: Invalid `typeof` comparison value
  ┌─ useValidTypeof.js:1:16
  │
1 │ typeof foo === baz
  │                --- not a string literal

typeof foo == 5

warning[useValidTypeof]: Invalid `typeof` comparison value
  ┌─ useValidTypeof.js:1:15
  │
1 │ typeof foo == 5
  │               - not a string literal

typeof foo == -5

warning[useValidTypeof]: Invalid `typeof` comparison value
  ┌─ useValidTypeof.js:1:15
  │
1 │ typeof foo == -5
  │               -- not a string literal

Valid

typeof foo === "string"

typeof bar == "undefined"

typeof bar === typeof qux