Basic JavaScript encoding Mode

1. variable definition
// General statement
Var a = 0;
Var B = 1;
Var c = 'xxx ';
 
// Recommended statement
Var a = 0,
B = 1,
C = 'xxx ';
 
2. Try to use the literal

// General statement
Var obj = new Object ();
Obj. a = 'a ';
Obj. B = 'bb ';
Obj. c = 'cc ';
 
Var arr = new Array ();
 
// Recommended statement
Var obj = {
A: 'A ',
B: 'bb'
};
 
Var arr = [];
 
Function getXX (index ){
Return ['A', 'bb ', 'XX', 55, 'xxb'] (index );
}
 
Function getMessage (code ){
Return {
404: 'xxx ',
500: 'xxx'
} [Code];
}
　　
3. Regular Expressions

Var regex = new RegExp ('someting ');
 
// Use the constructor only when the regular expression may change
Var cls = 'someclass ',
Regex = new RegExp (cls + '\ s *', 'ig '); // only for dynamic regexs
 
// Use the literal in other cases
Var regex =/someting/ig;
　　
4. Set the default value (personal feeling typeof)

// Default values
Var arg = arg | 'default'; // fallback
 
Document. getElementById ('test'). onclick = function (event ){
Var event = event | window. event;
};
 
Function getX (){
Return a + 1 | 'default ';
} <BR> function getY (B) {<BR> return typeof B! = "Undefined "? B: 'default'; <BR>}
 
5. Condition judgment

// Conditions
Answer = obj & obj. xx & obj. xx. xxx;
 
// Continuous judgment
If (obj & obj. xx & obj. xx. xxx ){
// Do something
}
 
If (obj. xx ){
// Do something
}
 
If (! Obj ){
// Do something
}
 
// Use full-level judgment
If (a = B ){
// Do something
}
 
// Try not to check the browser. Only check whether the features to be used are supported.
If (document. getElementById ){
// Ability detect
}
　　
6. Ternary Operators

// Ternary
Check? Value1: value2;
 
// The ternary operators are more concise.
Var foo = (condition )? Value1: value2;
 
Function xx (){
If (condition ){
Return value1;
} Else {
Return value2;
}
}
 
Function xx (){
Return (condition )? Value1: value2;
}
 
// Format the ternary Operator
Foo = predicate? "One ":
Predicate? "Two ":
"Default"; // format
　　
7. Insert iteration values

// Insert iteration
Var name = value [I];
I ++;
 
// Insert the iteration value directly
Var name = value [I ++];
　　
8. DOM operations

// DOM Operation
El. style. display = 'none'; // offline
// Operation
El. style. display = 'block ';
 
// Use the document fragment to perform better operations on www.2cto.com
Var fragment = document. createDocumentFragment (); // better
 
El. innerHTML = ''; // fast remove all children, but may leaks memory
El. innerHTML = 'xxx'; // OK, use it!
 
// Handle NodeList with caution
Var images = document. getElementsByTagName ('img '); // be careful! Dynamic list
　　
9. Event proxy

// Use event proxy to listen for events on the outer Element
Document. getElementById ('LIST'). onclick = function (evt ){
Var evt = evt | window. event,
Target = evt.tar get | evt. srcElement;
 
If (target. id = 'dn1 '){
// Do something
}
}
　　
10. namespace

// An Object as a Namespace
Var MYAPP = {};
MYAPP. dom. get = function (id ){};
MYAPP.style.css = function (el, style ){};
 
MYAPP. namespace ('event ');
　　
11. Chain Operations

// Chaining operation: return this
Function setValue (el, value ){
El. value = value;
Return this;
}
 
Var obj = new MYAPP. dom. Element ('span ');
Obj. setText ('hello ')
. SetStyle ('color', 'red ')
. SetStyle ('font', 'verdana ');
　　
12. Private Scope

// Function
(Function (){
Var _ private = 'cant see Me ';
 
})();
 
(Function ($ ){
$ ('# Xxb'). click (function (){});
}) (JQuery );
　　
13. Configuration object

// Configure Object
Function foo (id, conf, null, null ){
// Do somethin
}
 
Foo ('bar ',{
Key1: 1,
Key2: 2
});
　　
14. type conversion

// Type Conversion
+ '010 '= 10;
Number ('010 ') = 10;
ParseInt ('010 ', 10) = 10;
10 + ''= '10 ';
 
+ New Date () // timestamp
+ New Date;
　　
15. Extended prototype

// It is used only when forward compatibility is required. In other cases, it is not recommended to extend the prototype object.
Array. prototype. forEach = function (){
// Only for forward compatible
};
　　
16. Cyclic Optimization

// Cache
For (var I = 0, j = document. getElementsByTagName ('A'). length; i0; I --){
// Maybe faster
}
 
// It is said to be the fastest
While (I --){
// Maybe fastest
}
　　
17. Try to use the new feature

Array. forEach ();
GetElementsByClassName ();
QuerySlectorAll ();
 
// First, check whether new features are supported.
If (document. getElementsByClassName ){
// Use
} Else {
// Your implementations
}
　　
18. inert Loading

// Only judge once. You do not need to judge if you call this function again
Function lazyDef (){
If (condition1 ){
LazyDef = function (){};
} Else if (condition2 ){
LazyDef = function (){};
}
Return lazyDef ();
}
　　
19. Private functions and public methods

Var MYAPP = {};
 
MYAPP. dom = (function (){
Var _ setStyle = function (el, prop, value ){
Console. log ('setstyle ');
};
 
Return {
SetStyle: _ setStyle
};
})();
 
// When MYAPP. dom. setStyle is accidentally overwritten, _ setStyle is still available internally
　　
20. debugging

// Try to use it. You can input multiple parameters and output the concatenated string.
Console. log ('XX', 'XX ','...');
Console. dir (someObj );
Console. dirxml (someDom );
Console. time ('timer ');
Console. warn ('xxx ');
 
// Encapsulation ensures that accidental release will not cause problems, but the row number may be faulty when an error is reported.
Function msg (msg ){
If (console & console. log ){
Console. log (msg); // wrong line number
}
}

 

 

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