Find JavaScript code that changes existing objects or arrays, then replace those updates with modified copies. Review shared state and browser behavior to make data changes easier to trace and check fixes in context.
Use when reviewing scripts, client components, bundles, or runtime behavior related to Prefer immutable data patterns. Inspect both source code and the browser execution path so fixes target the real bottleneck or bug.
Review the instructions the agent will receive before you install.
Mutating shared objects makes it impossible to track where a value changed. When you update state immutably, each version of the data is a separate object — you can compare references to detect changes, time-travel debug, and know exactly which part of your code changed the data.
Find all places in this code where objects or arrays are mutated in place. Flag direct property assignments on function parameters and push/splice on arrays.
Replace in-place mutations with immutable patterns using spread operators and non-mutating array methods.
Explain immutable data patterns, why mutation causes bugs in shared state, and how spread and array methods enable immutability.
Review scripts, client components, and browser execution paths related to Prefer immutable data patterns. Flag exact imports, event handlers, runtime side effects, or blocking operations that violate the rule, and state how the change should be verified in the browser.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/javascript/immutable-patterns
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Create and review custom 404 pages that help visitors recover from broken or moved links through search and navigation. Check the rendered page and HTTP response so missing content returns a proper 404 status.
Audit or create a dedicated About page that explains a website’s purpose and identifies its people or organization. Review the rendered output and supporting information, including expertise and contact details, to find gaps.
Review and add automated accessibility checks for components, pages, and continuous integration workflows. Use axe-based tools to detect structural and attribute issues, while identifying checks that still need keyboard or screen reader testing.
Review sign-in, registration, multi-factor authentication, and account recovery for accessibility barriers. Find blocked paste, difficult code entry, and inaccessible backup methods, then suggest authentication paths that support password managers, autofill, or device approval.
Review form errors, success messages, and live updates so screen reader users receive important notifications. Check the HTML delivered to the browser, announcement settings, display duration, and dismissal controls, then identify specific elements that need changes.
Review HTML tables so screen reader users can understand how headers and data relate. Check header markup, table descriptions, and merged cells, then identify specific fixes and ways to verify them.