--- /dev/null
+/**
+ * @fileoverview Rule to disallow Math.pow in favor of the ** operator
+ * @author Milos Djermanovic
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("./utils/ast-utils");
+const { CALL, ReferenceTracker } = require("eslint-utils");
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+const PRECEDENCE_OF_EXPONENTIATION_EXPR = astUtils.getPrecedence({ type: "BinaryExpression", operator: "**" });
+
+/**
+ * Determines whether the given node needs parens if used as the base in an exponentiation binary expression.
+ * @param {ASTNode} base The node to check.
+ * @returns {boolean} `true` if the node needs to be parenthesised.
+ */
+function doesBaseNeedParens(base) {
+ return (
+
+ // '**' is right-associative, parens are needed when Math.pow(a ** b, c) is converted to (a ** b) ** c
+ astUtils.getPrecedence(base) <= PRECEDENCE_OF_EXPONENTIATION_EXPR ||
+
+ // An unary operator cannot be used immediately before an exponentiation expression
+ base.type === "UnaryExpression"
+ );
+}
+
+/**
+ * Determines whether the given node needs parens if used as the exponent in an exponentiation binary expression.
+ * @param {ASTNode} exponent The node to check.
+ * @returns {boolean} `true` if the node needs to be parenthesised.
+ */
+function doesExponentNeedParens(exponent) {
+
+ // '**' is right-associative, there is no need for parens when Math.pow(a, b ** c) is converted to a ** b ** c
+ return astUtils.getPrecedence(exponent) < PRECEDENCE_OF_EXPONENTIATION_EXPR;
+}
+
+/**
+ * Determines whether an exponentiation binary expression at the place of the given node would need parens.
+ * @param {ASTNode} node A node that would be replaced by an exponentiation binary expression.
+ * @param {SourceCode} sourceCode A SourceCode object.
+ * @returns {boolean} `true` if the expression needs to be parenthesised.
+ */
+function doesExponentiationExpressionNeedParens(node, sourceCode) {
+ const parent = node.parent;
+
+ const needsParens = (
+ parent.type === "ClassDeclaration" ||
+ (
+ parent.type.endsWith("Expression") &&
+ astUtils.getPrecedence(parent) >= PRECEDENCE_OF_EXPONENTIATION_EXPR &&
+ !(parent.type === "BinaryExpression" && parent.operator === "**" && parent.right === node) &&
+ !((parent.type === "CallExpression" || parent.type === "NewExpression") && parent.arguments.includes(node)) &&
+ !(parent.type === "MemberExpression" && parent.computed && parent.property === node) &&
+ !(parent.type === "ArrayExpression")
+ )
+ );
+
+ return needsParens && !astUtils.isParenthesised(sourceCode, node);
+}
+
+/**
+ * Optionally parenthesizes given text.
+ * @param {string} text The text to parenthesize.
+ * @param {boolean} shouldParenthesize If `true`, the text will be parenthesised.
+ * @returns {string} parenthesised or unchanged text.
+ */
+function parenthesizeIfShould(text, shouldParenthesize) {
+ return shouldParenthesize ? `(${text})` : text;
+}
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+ meta: {
+ type: "suggestion",
+
+ docs: {
+ description: "disallow the use of `Math.pow` in favor of the `**` operator",
+ category: "Stylistic Issues",
+ recommended: false,
+ url: "https://eslint.org/docs/rules/prefer-exponentiation-operator"
+ },
+
+ schema: [],
+ fixable: "code",
+
+ messages: {
+ useExponentiation: "Use the '**' operator instead of 'Math.pow'."
+ }
+ },
+
+ create(context) {
+ const sourceCode = context.getSourceCode();
+
+ /**
+ * Reports the given node.
+ * @param {ASTNode} node 'Math.pow()' node to report.
+ * @returns {void}
+ */
+ function report(node) {
+ context.report({
+ node,
+ messageId: "useExponentiation",
+ fix(fixer) {
+ if (
+ node.arguments.length !== 2 ||
+ node.arguments.some(arg => arg.type === "SpreadElement") ||
+ sourceCode.getCommentsInside(node).length > 0
+ ) {
+ return null;
+ }
+
+ const base = node.arguments[0],
+ exponent = node.arguments[1],
+ baseText = sourceCode.getText(base),
+ exponentText = sourceCode.getText(exponent),
+ shouldParenthesizeBase = doesBaseNeedParens(base),
+ shouldParenthesizeExponent = doesExponentNeedParens(exponent),
+ shouldParenthesizeAll = doesExponentiationExpressionNeedParens(node, sourceCode);
+
+ let prefix = "",
+ suffix = "";
+
+ if (!shouldParenthesizeAll) {
+ if (!shouldParenthesizeBase) {
+ const firstReplacementToken = sourceCode.getFirstToken(base),
+ tokenBefore = sourceCode.getTokenBefore(node);
+
+ if (
+ tokenBefore &&
+ tokenBefore.range[1] === node.range[0] &&
+ !astUtils.canTokensBeAdjacent(tokenBefore, firstReplacementToken)
+ ) {
+ prefix = " "; // a+Math.pow(++b, c) -> a+ ++b**c
+ }
+ }
+ if (!shouldParenthesizeExponent) {
+ const lastReplacementToken = sourceCode.getLastToken(exponent),
+ tokenAfter = sourceCode.getTokenAfter(node);
+
+ if (
+ tokenAfter &&
+ node.range[1] === tokenAfter.range[0] &&
+ !astUtils.canTokensBeAdjacent(lastReplacementToken, tokenAfter)
+ ) {
+ suffix = " "; // Math.pow(a, b)in c -> a**b in c
+ }
+ }
+ }
+
+ const baseReplacement = parenthesizeIfShould(baseText, shouldParenthesizeBase),
+ exponentReplacement = parenthesizeIfShould(exponentText, shouldParenthesizeExponent),
+ replacement = parenthesizeIfShould(`${baseReplacement}**${exponentReplacement}`, shouldParenthesizeAll);
+
+ return fixer.replaceText(node, `${prefix}${replacement}${suffix}`);
+ }
+ });
+ }
+
+ return {
+ Program() {
+ const scope = context.getScope();
+ const tracker = new ReferenceTracker(scope);
+ const trackMap = {
+ Math: {
+ pow: { [CALL]: true }
+ }
+ };
+
+ for (const { node } of tracker.iterateGlobalReferences(trackMap)) {
+ report(node);
+ }
+ }
+ };
+ }
+};
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