You dont know js prototypal inheritance code#
You dont know js prototypal inheritance series#

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You dont know js prototypal inheritance code#

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You dont know js prototypal inheritance series#

The concept of function inheritance was first proposed by Douglas Crockford, but it has been used in JavaScript for a long time.The worldwide best selling You Don't Know JS book series is back for a 2nd edition: You Don't Know JS Yet.

Function inheritance works by creating an object from a factory function and adding properties directly to the object to extend the object (using concatenated inheritance). If a function is neither a constructor nor a class, it is called a factory function. Function inheritance: in JavaScript, any function can be used to create objects.Create() to achieve the same purpose, or mix it with splicing inheritance, so that multiple prototypes can be reduced to a single agent, or you can continue to expand after an object instance is created. The instance is created by using the new keyword, and the constructor.prototype is linked back and forth to form an inheritance chain. In this way, a prototype chain is formed, which looks up along the agent chain until the attribute is found, or the root agent object.prototype is found. The proxy prototype itself will have its own proxy prototype. If a property does not exist in the current object, it looks for its proxy prototype. Prototype proxy: in JavaScript, an object may contain a reference to the prototype, which is called a proxy.In the above example of object combination, splicing inheritance is adopted. Extend() provided by undercore / lodash or $. Before ES6, it was usually implemented using. The copied prototype is often called mixins. Splicing inheritance: it is a pattern that copies attributes directly from one object to another.There are three kinds of object-oriented design methods based on prototype. Unlike most other languages, JavaScript is based on a prototype object system, not a class.

JavaScript you donвЂ™t know Based on prototype chain Therefore, instead of calling inheritance, delegation is more accurate. Instead, JavaScript just creates an association between two objects, so that one object can access the properties and functions of another object through delegation. However, JavaScript does not copy the properties of objects by default. This kind of search track is like a long chain, and because prototype plays the role of link in the rules of the game, we call this chain of instance and prototype prototype prototype as prototype chain Search track: person1 - > animal2 - > animal. If there is no such thing in animal2, the program will not lose heart at this time, and it will continue to look for the prototype object in animal2

Prototype is actually animal2, that is to say, we will find the property P1 in animal2 ДЈ). First, find it in the internal attribute of instance1 Дў). In view of the effectiveness of the above rules, if an attempt is made to refer to an attribute of the instance person1 constructed by person:ДЎ). If you point a prototype object to an instance of another typeвЂ¦ Interesting things happen If not, the prototype will be found until the top level. When reading the properties of an instance, if not found, the properties in the prototype associated with the object will be found.