no-sparse-arrays.jsā¢1.48 kB
/**
* @fileoverview Disallow sparse arrays
* @author Nicholas C. Zakas
*/
"use strict";
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../types').Rule.RuleModule} */
module.exports = {
meta: {
type: "problem",
docs: {
description: "Disallow sparse arrays",
recommended: true,
url: "https://eslint.org/docs/latest/rules/no-sparse-arrays",
},
schema: [],
messages: {
unexpectedSparseArray: "Unexpected comma in middle of array.",
},
},
create(context) {
//--------------------------------------------------------------------------
// Public
//--------------------------------------------------------------------------
return {
ArrayExpression(node) {
if (!node.elements.includes(null)) {
return;
}
const { sourceCode } = context;
let commaToken;
for (const [index, element] of node.elements.entries()) {
if (index === node.elements.length - 1 && element) {
return;
}
commaToken = sourceCode.getTokenAfter(
element ?? commaToken ?? sourceCode.getFirstToken(node),
astUtils.isCommaToken,
);
if (element) {
continue;
}
context.report({
node,
loc: commaToken.loc,
messageId: "unexpectedSparseArray",
});
}
},
};
},
};