valid-typeof.md

enforce comparing typeof expressions against valid strings (valid-typeof)

For a vast majority of use cases, the result of the typeof operator is one of the following string literals: "undefined", "object", "boolean", "number", "string", "function" and "symbol". It is usually a typing mistake to compare the result of a typeof operator to other string literals.

Rule Details

This rule enforces comparing typeof expressions to valid string literals.

Examples of incorrect code for this rule:

/*eslint valid-typeof: "error"*/

typeof foo === "strnig"
typeof foo == "undefimed"
typeof bar != "nunber"
typeof bar !== "fucntion"

Examples of correct code for this rule:

/*eslint valid-typeof: "error"*/

typeof foo === "string"
typeof bar == "undefined"
typeof foo === baz
typeof bar === typeof qux

When Not To Use It

You may want to turn this rule off if you will be using the typeof operator on host objects.