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| /** | |
| * @fileoverview Ensures that the results of typeof are compared against a valid string | |
| * @author Ian Christian Myers | |
| */ | |
| "use strict"; | |
| //------------------------------------------------------------------------------ | |
| // Rule Definition | |
| //------------------------------------------------------------------------------ | |
| module.exports = { | |
| meta: { | |
| type: "problem", | |
| docs: { | |
| description: "enforce comparing `typeof` expressions against valid strings", | |
| category: "Possible Errors", | |
| recommended: true, | |
| url: "https://eslint.org/docs/rules/valid-typeof" | |
| }, | |
| schema: [ | |
| { | |
| type: "object", | |
| properties: { | |
| requireStringLiterals: { | |
| type: "boolean", | |
| default: false | |
| } | |
| }, | |
| additionalProperties: false | |
| } | |
| ], | |
| messages: { | |
| invalidValue: "Invalid typeof comparison value.", | |
| notString: "Typeof comparisons should be to string literals." | |
| } | |
| }, | |
| create(context) { | |
| const VALID_TYPES = ["symbol", "undefined", "object", "boolean", "number", "string", "function", "bigint"], | |
| OPERATORS = ["==", "===", "!=", "!=="]; | |
| const requireStringLiterals = context.options[0] && context.options[0].requireStringLiterals; | |
| /** | |
| * Determines whether a node is a typeof expression. | |
| * @param {ASTNode} node The node | |
| * @returns {boolean} `true` if the node is a typeof expression | |
| */ | |
| function isTypeofExpression(node) { | |
| return node.type === "UnaryExpression" && node.operator === "typeof"; | |
| } | |
| //-------------------------------------------------------------------------- | |
| // Public | |
| //-------------------------------------------------------------------------- | |
| return { | |
| UnaryExpression(node) { | |
| if (isTypeofExpression(node)) { | |
| const parent = context.getAncestors().pop(); | |
| if (parent.type === "BinaryExpression" && OPERATORS.indexOf(parent.operator) !== -1) { | |
| const sibling = parent.left === node ? parent.right : parent.left; | |
| if (sibling.type === "Literal" || sibling.type === "TemplateLiteral" && !sibling.expressions.length) { | |
| const value = sibling.type === "Literal" ? sibling.value : sibling.quasis[0].value.cooked; | |
| if (VALID_TYPES.indexOf(value) === -1) { | |
| context.report({ node: sibling, messageId: "invalidValue" }); | |
| } | |
| } else if (requireStringLiterals && !isTypeofExpression(sibling)) { | |
| context.report({ node: sibling, messageId: "notString" }); | |
| } | |
| } | |
| } | |
| } | |
| }; | |
| } | |
| }; |