JavaScript Advanced Programming Reading Notes 11 Built-in Object Global

JavaScript Advanced Programming Reading Notes 11 Built-in Object Global_javascript Skills

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Release： 2016-05-16 17:55:46

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Built-in objects
Definition: All objects provided by the ECMAScript implementation that are independent of the host environment and appear when the ECMAScript program starts executing.

It can be seen from the definition that developers do not have to explicitly instantiate the built-in object, it has already been instantiated. Only two built-in objects are defined in ECMAScript-262, namely Global and Math

Global
The Global object is the most special object in ECMAScript, because in fact it does not exist at all.

Since there are no independent objects in ECMAScript, all functions must be methods of an object, such as the aforementioned isNaN(), isFinite(), parseInt() and parseFloat(), etc. Is a method of Global object.

Escape(), encodeURI(), encodeURIComponent(), unescape(), decodeURI(), decodeURIComponent(), eval(), etc. are all Global methods.

escape() && encodeURI() && encodeURIComponent()
　These methods are used to encode strings.

There are 69 unencoded characters in escape: *, , -, ., /, @, _, 0-9, a-z, A-Z

There are 82 unencoded characters in encodeURI: !, #,$,&,',(,),*, ,,,-,.,/,:,;,=,?,@,_,~,0-9,a-z,A-Z

encodeURIComponent does not encode 71 characters: !, ', (,), *, -, ., _, ~, 0-9, a-z, A-Z

　escape(): Not recommended, Deprecated

encodeURI(): Encode the URL, example:

Copy code The code is as follows :

 
encodeURI("http://www.jb51.net/a file with spaces.html") 
// outputs http://www.jb51.net/a file with spaces.html 

encodeURIComponent(): Encode parameters, example:

Copy code Code As follows:

 
param1 = encodeURIComponent("http://xyz.com/?a=12&b=55") 
url ="http://domain.com/?param1=" param1 "¶m2=99"; 
// outputs http://www.domain.com/?param1=http://xyz.com/�a=12&b=55¶m2=99 

unescape() && decodeURI() && decodeURIComponent()
　These methods are used to decode strings.

eval()
eval() may be the most powerful method in the ECMAScript language. This method is like the entire JavaScript interpreter, accepting one parameter, which is the function to be executed. ECMAScript (or JavaScript) string.

Example:

Copy code The code is as follows:

 
var msg="Hello world"; 
eval("alert(msg)");//alert "Hello world" 

Note that the eval() function is very powerful, but it is also very dangerous. Especially when eval is used to execute user input, it may be injected by code.

All properties of Global object
Global not only has methods, it also has properties, all properties of Global object:

属性	说明
undefined	Undifined类型的字面量
NaN	非数的专用数值
Infinity	无穷大值的专用数值
Object	Object的构造函数
Array	Array 的构造函数
Function	Function 的构造函数
Boolean	Boolean 的构造函数
String	String 的构造函数
Number	Number 的构造函数
Date	Date 的构造函数
RegExp	RegExp 的构造函数
Error	Error 的构造函数
EvalError	EvalError 的构造函数
RangeError	RangeError 的构造函数
ReferenceError	ReferenceError 的构造函数
SyntaxError	SyntaxError 的构造函数
TypeError	TypeError 的构造函数
URIError	URIError 的构造函数

Author: Tian Xingjian, self-improvement

Source: http://artwl.cnblogs.com