JavaScript

Found non-compliant syntax. Confirm that there are no syntax errors before committing your code to a version control system.

When defining a route, it's not necessary to specify the path option if it matches the route name.

URLs starting with javascript: are a dangerous attack surface because it's easy to accidentally include the unsanitized output in a tag like <a href> and create a security hole for XSS. The developers can use the React event handlers e.g. onChange, onClick etc.

Control characters are special, invisible characters in the ASCII range 0-31. These characters are rarely used in JavaScript strings, so a regular expression containing these characters is most likely a mistake.

An invalid pattern in a regular expression literal results in a SyntaxError when the code is parsed, but an invalid string in a RegExp constructor throws a SyntaxError only when the code is executed.

It is recommended to use head as a function as it provides access to more data through this.

Re-assigning a variable that was declared with the const keyword can lead to a TypeError.

this.$slots.default was an array of VNode in Vue.js 2.x, but changed to a function that returns an array of VNode in Vue.js 3.x.

There should not be name collisions between Vue components, standard HTML elements and built-in components.

Unused properties should be eliminated.

The $cookieStore service has been deprecated since Angular 1.4. Use the $cookies service instead.

Create clearer code by disallowing the bad practice of creating a label that shares a name with a variable that is in scope.

Avoid using needs to load other controllers. Inject the required controller instead. needs was deprecated in ember 1.x and removed in 2.0.

The only good place to assign this.state is in an ES6 class component constructor.

It is not recommended to mutate this.state directly, as calling setState() afterward may replace the mutation. You should treat this.state as if it were immutable.

If more than one parameter in the function definition has the same name, the last occurrence "shadows" the preceding occurrences. A duplicated name might be a typo, and may confuse anyone reading the code.

When writing asynchronous code, it is possible to create subtle race condition bugs. Consider the following example:

Function declarations (with the function keyword) and variable declarations should preferably be in the root of a program or the body of a function. Having nested function declarations inside blocks may have unexpected results at runtime due to hoisting.

This rule is aimed at disallowing exports = {}, but allows module.exports = exports = {} to avoid conflict with node/exports-style rule's allowBatchAssign option.

The var keyword is soft-deprecated, and should not be used to redeclare existing variables.

An unused expression that does not affect the state of the program indicates a logic error.