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4 |
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5 | "use strict";
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6 |
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7 |
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8 |
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9 |
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10 |
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11 | module.exports = {
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12 | meta: {
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13 | docs: {
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14 | description: "enforce comparing `typeof` expressions against valid strings",
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15 | category: "Possible Errors",
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16 | recommended: true
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17 | },
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18 |
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19 | schema: [
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20 | {
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21 | type: "object",
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22 | properties: {
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23 | requireStringLiterals: {
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24 | type: "boolean"
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25 | }
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26 | },
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27 | additionalProperties: false
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28 | }
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29 | ]
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30 | },
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31 |
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32 | create(context) {
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33 |
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34 | const VALID_TYPES = ["symbol", "undefined", "object", "boolean", "number", "string", "function"],
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35 | OPERATORS = ["==", "===", "!=", "!=="];
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36 |
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37 | const requireStringLiterals = context.options[0] && context.options[0].requireStringLiterals;
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38 |
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39 | |
40 |
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41 |
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42 |
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43 |
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44 | function isTypeofExpression(node) {
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45 | return node.type === "UnaryExpression" && node.operator === "typeof";
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46 | }
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47 |
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48 |
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49 |
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50 |
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51 |
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52 | return {
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53 |
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54 | UnaryExpression(node) {
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55 | if (isTypeofExpression(node)) {
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56 | const parent = context.getAncestors().pop();
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57 |
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58 | if (parent.type === "BinaryExpression" && OPERATORS.indexOf(parent.operator) !== -1) {
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59 | const sibling = parent.left === node ? parent.right : parent.left;
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60 |
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61 | if (sibling.type === "Literal" || sibling.type === "TemplateLiteral" && !sibling.expressions.length) {
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62 | const value = sibling.type === "Literal" ? sibling.value : sibling.quasis[0].value.cooked;
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63 |
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64 | if (VALID_TYPES.indexOf(value) === -1) {
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65 | context.report(sibling, "Invalid typeof comparison value.");
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66 | }
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67 | } else if (requireStringLiterals && !isTypeofExpression(sibling)) {
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68 | context.report(sibling, "Typeof comparisons should be to string literals.");
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69 | }
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70 | }
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71 | }
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72 | }
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73 |
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74 | };
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75 |
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76 | }
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77 | };
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