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Rest parameters are similar to Javascript's arguments object, which is an array-like object that contains all of the parameters (named and unnamed) in the current function call. Unlike arguments , however, rest parameters are true Array objects, so methods such as .slice() and .sort() can be used on them directly.
The Event object provides a lot of information about a particular event, including information about target element, key pressed, mouse button pressed, mouse position, etc. Unfortunately, there are very serious browser incompatibilities in this area. Hence only the W3C Event object is discussed in this article.
In JavaScript, an object is an associative array, augmented with a prototype (see below); each key provides the name for an object property, and there are two syntactical ways to specify such a name: dot notation (obj.x = 10) and bracket notation (obj['x'] = 10). A property may be added, rebound, or deleted at run-time.
Common exceptions include an invalid argument (e.g. value is outside of the domain of a function), [5] an unavailable resource (like a missing file, [6] a network drive error, [7] or out-of-memory errors [8]), or that the routine has detected a normal condition that requires special handling, e.g., attention, end of file. [9]
JavaScript has a deprecated Object.observe function that was a more accurate implementation of the observer pattern. [10] This would fire events upon change to the observed object. Without the deprecated Object.observe function, the pattern may be implemented with more explicit code: [11]
In object-oriented programming, a class defines the shared aspects of objects created from the class. The capabilities of a class differ between programming languages, but generally the shared aspects consist of state and behavior that are each either associated with a particular object or with all objects of that class.
In Self, an object may have multiple or no parents, [34] but in the most popular prototype-based language, Javascript, every object has one prototype link (and only one). New objects can be created based on already existing objects chosen as their prototype.
Copy constructors define the actions performed by the compiler when copying class objects. A Copy constructor has one formal parameter that is the type of the class (the parameter may be a reference to an object). It is used to create a copy of an existing object of the same class.