JavaScript exploration: Constructor

In addition to creating objects, constructor also does another useful thing-automatically creates

In addition to creating objects, constructor has also done another useful thing: prototype object is automatically set for the newly created object ). The prototype object is stored in the ConstructorFunction. prototype attribute.

For example, if we rewrite the previous example and use the constructor to create objects "B" and "c", then object "a" assumes the role "Foo. prototype:

// Constructor function Foo (y) {// constructor will create an object in a specific mode: the object to be created will have the "y" attribute this. y = y;} // "Foo. prototype "stores the prototype reference of the new object // so we can use it to define the inheritance and sharing attributes or methods. Therefore, like in the preceding example, we have the following code: // inherit the property "x" Foo. prototype. x = 10; // The Inheritance Method "calculate" Foo. prototype. calculate = function (z) {return this. x + this. y + z ;}; // use the foo mode to create "B" and "c" var B = new Foo (20); var c = new Foo (30 ); // call the inherited method B. calculate (30); // 60c. calculate (40); // 80 // Let's see if the expected property console is used. log (B. _ proto _ = Foo. prototype, // true c. _ proto _ = Foo. prototype, // true // "Foo. prototype "automatically creates a special attribute" constructor "// points to the constructor itself of a // instance" B "and" c "can be found through authorization and used to detect its own constructor B. constructor = Foo, // true c. constructor = Foo, // true Foo. prototype. constructor = Foo // true B. calculate = B. _ proto __. calculate, // true B. _ proto __. calculate = Foo. prototype. calculate // true );

The above code can be expressed as the following link:

Relationships between constructors and objects

The preceding figure shows that each object has a prototype. the constructor Foo also has its own _ proto __, that is, Function. prototype, while Function. prototype _ proto _ points to Object. prototype. reapply, Foo. prototype is only an explicit attribute, that is, the _ proto _ attribute of B and c.

The complete and detailed explanation of this question includes two parts:

• Object-Oriented Programming-general theory (OOP. The general theory) describes different object-oriented paradigms and stylistics and compares them with ECMAScript.
• Object-Oriented Programming. ECMAScript implementation (OOP. ECMAScript implementation) specifically describes Object-Oriented Programming in ECMAScript.

Now that we know the basic object principle, let's take a look at the program execution environment [runtime program execution] In ECMAScript. this is commonly referred to as "execution context stack" [execution context stack]. Each element can be abstracted as an object. You may have discovered that, right. In ECMAScript, You can see objects almost everywhere.

Additional reading

The topic list of this article is as follows:

1. How should we understand the working principle of the JavaScript engine?
2. JavaScript exploration: the importance of writing maintainable code
3. JavaScript exploration: exercise caution when using global variables
4. JavaScript exploration: var pre-parsing and side effects
5. JavaScript exploration: for Loop (for Loops)
6. JavaScript exploration: for-in loop (for-in Loops)
7. Exploring JavaScript: Prototypes is too powerful
8. JavaScript: eval () is the devil"
9. JavaScript exploration: Using parseInt () for Numerical Conversion
10. Exploring JavaScript: Basic coding specifications
11. JavaScript exploration: function declaration and function expression
12. JavaScript exploration: Name function expressions
13. JavaScript: function name in the debugger
14. JavaScript: JScript Bug
15. JavaScript exploration: Memory Management of JScript
16. Exploring JavaScript: SpiderMonkey's quirks
17. JavaScript exploration: an alternative solution to naming function expressions
18. JavaScript exploration: Object
19. JavaScript exploration: Prototype chain
20. JavaScript exploration: Constructor
21. JavaScript probing: executable context Stack
22. Execution context 1: Variable object and activity object
23. Execution context 2: Scope chain Scope Chains
24. Execution context 3: Closure Closures
25. Execution context 4: This pointer
26. Exploring JavaScript: Powerful prototype and prototype chain
27. JavaScript Functions 1: function declaration
28. JavaScript function 2: function expressions
29. JavaScript function 3: function expressions in a group
30. JavaScript function 4: function Constructor
31. JavaScript variable object 1: VO Declaration
32. JavaScript variable object 2: VO in different execution contexts
33. JavaScript variable object 3: two stages of execution Context
34. JavaScript variable object IV: Variables
35. Property of the JavaScript variable object __parent _
36. JavaScript scope chain 1: Scope chain Definition
37. JavaScript scope chain 2: function Lifecycle
38. JavaScript scope chain 3: Scope chain features
39. JavaScript closure 1: Introduction to closures
40. JavaScript closure 2: Implementation of closure
41. JavaScript closure 3: Closure usage

This article is available at http://www.nowamagic.net/librarys/veda/detail/1642.