JavaScript exploration: Name function expressions

Function expressions are still very common in practical applications. In web development, a common pattern is based on a certain feature.

Function expressions are still very common in practical applications. In web development, a common pattern is to disguise function definitions based on tests on certain features to achieve performance optimization, however, because this method is in the same scope, function expressions must be used:

// The Code comes from the APE Javascript library (http://dhtmlkitchen.com/ape/) var contains = (function () {var docEl = document.doc umentElement; if (typeof docEl. compareDocumentPosition! = 'Undefined') {return function (el, B) {return (el. compareDocumentPosition (B) & 16 )! = 0 ;};} else if (typeof docEl. contains! = 'Undefined') {return function (el, B) {return el! = B & el. contains (B) ;}return function (el, B) {if (el = B) return false; while (el! = B & (B = B. parentNode )! = Null); return el = B ;};})();

When it comes to the naming function expression, it must have a name. In the preceding example, var bar = function foo () {}; is a valid naming function expression, but remember one thing: this name is valid only in the scope of the newly defined function, because the specification stipulates that the identifier cannot be valid in the peripheral scope:

Var f = function foo () {return typeof foo; // foo is valid within the internal scope}; // foo is used externally as invisible typeof foo; // "undefined" f (); // "function"

In this case, what is the use of the name function expression? Why?

As we said at the beginning: to give it a name is to make the debugging process more convenient, because during debugging, if each item in the call Stack has its own name, the debugging process is so cool that you may feel different.

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/1634.