2 * @fileoverview A rule to suggest using of the spread operator instead of `.apply()`.
3 * @author Toru Nagashima
8 const astUtils = require("./utils/ast-utils");
10 //------------------------------------------------------------------------------
12 //------------------------------------------------------------------------------
15 * Checks whether or not a node is a `.apply()` for variadic.
16 * @param {ASTNode} node A CallExpression node to check.
17 * @returns {boolean} Whether or not the node is a `.apply()` for variadic.
19 function isVariadicApplyCalling(node) {
21 astUtils.isSpecificMemberAccess(node.callee, null, "apply") &&
22 node.arguments.length === 2 &&
23 node.arguments[1].type !== "ArrayExpression" &&
24 node.arguments[1].type !== "SpreadElement"
29 * Checks whether or not `thisArg` is not changed by `.apply()`.
30 * @param {ASTNode|null} expectedThis The node that is the owner of the applied function.
31 * @param {ASTNode} thisArg The node that is given to the first argument of the `.apply()`.
32 * @param {RuleContext} context The ESLint rule context object.
33 * @returns {boolean} Whether or not `thisArg` is not changed by `.apply()`.
35 function isValidThisArg(expectedThis, thisArg, context) {
37 return astUtils.isNullOrUndefined(thisArg);
39 return astUtils.equalTokens(expectedThis, thisArg, context);
42 //------------------------------------------------------------------------------
44 //------------------------------------------------------------------------------
51 description: "require spread operators instead of `.apply()`",
52 category: "ECMAScript 6",
54 url: "https://eslint.org/docs/rules/prefer-spread"
61 preferSpread: "Use the spread operator instead of '.apply()'."
66 const sourceCode = context.getSourceCode();
69 CallExpression(node) {
70 if (!isVariadicApplyCalling(node)) {
74 const applied = astUtils.skipChainExpression(astUtils.skipChainExpression(node.callee).object);
75 const expectedThis = (applied.type === "MemberExpression") ? applied.object : null;
76 const thisArg = node.arguments[0];
78 if (isValidThisArg(expectedThis, thisArg, sourceCode)) {
81 messageId: "preferSpread"