no-loop-func.js

/**
 * @fileoverview Rule to flag creation of function inside a loop
 * @author Ilya Volodin
 */

"use strict";

//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------

/**
 * Gets the containing loop node of a specified node.
 *
 * We don't need to check nested functions, so this ignores those.
 * `Scope.through` contains references of nested functions.
 * @param {ASTNode} node An AST node to get.
 * @returns {ASTNode|null} The containing loop node of the specified node, or
 *      `null`.
 */
function getContainingLoopNode(node) {
    for (let currentNode = node; currentNode.parent; currentNode = currentNode.parent) {
        const parent = currentNode.parent;

        switch (parent.type) {
            case "WhileStatement":
            case "DoWhileStatement":
                return parent;

            case "ForStatement":

                // `init` is outside of the loop.
                if (parent.init !== currentNode) {
                    return parent;
                }
                break;

            case "ForInStatement":
            case "ForOfStatement":

                // `right` is outside of the loop.
                if (parent.right !== currentNode) {
                    return parent;
                }
                break;

            case "ArrowFunctionExpression":
            case "FunctionExpression":
            case "FunctionDeclaration":

                // We don't need to check nested functions.
                return null;

            default:
                break;
        }
    }

    return null;
}

/**
 * Gets the containing loop node of a given node.
 * If the loop was nested, this returns the most outer loop.
 * @param {ASTNode} node A node to get. This is a loop node.
 * @param {ASTNode|null} excludedNode A node that the result node should not
 *      include.
 * @returns {ASTNode} The most outer loop node.
 */
function getTopLoopNode(node, excludedNode) {