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 "getter functions must have no arguments" occurs when a getter is declared and the parameter list is non-empty.

The JavaScript exception "must call super constructor before using 'this' in derived class constructor" occurs when the super() is not called for a given derived class constructor, and the derived constructor tries to access the value of this, or the derived constructor has already returned and the return value is not an object.

The JavaScript exception "use of super property/member accesses only valid within methods or eval code within methods" occurs when the super.x or super[x] syntax is used outside of a method.

An expression statement is an expression used in a place where a statement is expected. The expression is evaluated and its result is discarded — therefore, it makes sense only for expressions that have side effects, such as executing a function or updating a variable.

The primitiveUnits attribute specifies the coordinate system for the various length values within the filter primitives and for the attributes that define the filter primitive subregion.

Method definition is a shorter syntax for defining a function property in an object initializer. It can also be used in classes.

The patternTransform attribute defines a list of transform definitions that are applied to a pattern tile.

the preserveAlpha attribute indicates how a <feConvolveMatrix> element handles alpha transparency.

The fill-rule attribute is a presentation attribute defining the algorithm to use to determine the inside part of a shape.