The JavaScript strict mode-only exception "for-in loop head declarations may not have initializers" occurs when the head of a for...in contains an initializer expression, such as for (var i = 0 in obj). This is not allowed in for-in loops in strict mode. In addition, lexical declarations with initializers like for (const i = 0 in obj) are not allowed outside strict mode either.

The JavaScript exception "invalid Array.prototype.sort argument" occurs when the argument of Array.prototype.sort() isn't either undefined or a function which compares its operands.

The JavaScript exception ""use strict" not allowed in function" occurs when a "use strict" directive is used at the top of a function with default parameters, rest parameters, or destructuring parameters.

The rx attribute defines a radius on the x-axis.

The JavaScript exception "missing } after property list" occurs when there is a mistake in the object initializer syntax somewhere. Might be in fact a missing curly bracket, but could also be a missing comma.

The JavaScript exception "missing variable name" is a common error. It is usually caused by omitting a variable name or a typographic error.

The Function() constructor creates Function objects. Calling the constructor directly can create functions dynamically, but suffers from security and similar (but far less significant) performance issues as eval(). However, unlike eval (which may have access to the local scope), the Function constructor creates functions which execute in the global scope only.

The Promise.all() static method takes an iterable of promises as input and returns a single Promise. This returned promise fulfills when all of the input's promises fulfill (including when an empty iterable is passed), with an array of the fulfillment values. It rejects when any of the input's promises rejects, with this first rejection reason.

The Object.entries() static method returns an array of a given object's own enumerable string-keyed property key-value pairs.

The Reflect.getOwnPropertyDescriptor() static method is like Object.getOwnPropertyDescriptor(). It returns a property descriptor of the given property if it exists on the object, undefined otherwise.