--- /dev/null
+/**
+ * @fileoverview Rule to flag when initializing to undefined
+ * @author Ilya Volodin
+ */
+
+"use strict";
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+ meta: {
+ type: "suggestion",
+
+ docs: {
+ description: "disallow initializing variables to `undefined`",
+ category: "Variables",
+ recommended: false,
+ url: "https://eslint.org/docs/rules/no-undef-init"
+ },
+
+ schema: [],
+ fixable: "code",
+
+ messages: {
+ unnecessaryUndefinedInit: "It's not necessary to initialize '{{name}}' to undefined."
+ }
+ },
+
+ create(context) {
+
+ const sourceCode = context.getSourceCode();
+
+ return {
+
+ VariableDeclarator(node) {
+ const name = sourceCode.getText(node.id),
+ init = node.init && node.init.name,
+ scope = context.getScope(),
+ undefinedVar = astUtils.getVariableByName(scope, "undefined"),
+ shadowed = undefinedVar && undefinedVar.defs.length > 0,
+ lastToken = sourceCode.getLastToken(node);
+
+ if (init === "undefined" && node.parent.kind !== "const" && !shadowed) {
+ context.report({
+ node,
+ messageId: "unnecessaryUndefinedInit",
+ data: { name },
+ fix(fixer) {
+ if (node.parent.kind === "var") {
+ return null;
+ }
+
+ if (node.id.type === "ArrayPattern" || node.id.type === "ObjectPattern") {
+
+ // Don't fix destructuring assignment to `undefined`.
+ return null;
+ }
+
+ if (sourceCode.commentsExistBetween(node.id, lastToken)) {
+ return null;
+ }
+
+ return fixer.removeRange([node.id.range[1], node.range[1]]);
+ }
+ });
+ }
+ }
+ };
+
+ }
+};