Javascript tips (updating ...)

1. determine the type of an object
 

 
If (typeof o = "object") & (O. constructor = Date) // then do something with the date object... if (typeof o = "object") & (O instanceof date) // then do something with the date object...
 

Table: Type-checking Variables

variable	typeof variable	variable. constructor
{An: "object"}	Object	Object
["an", "array"]	Object	array
function () {}	function	function
"a string"	string	string
55	Number	Number
true	Boolean	Boolean
new user ()	Object	User

2. string connection in Javascript
as we all know, in C #, stringbuilder is more efficient than string. concat efficiency is several orders of magnitude higher
For details, refer to: string. concat versus text. stringbuilder
the same problem exists in Javascript. A small test was conducted to check the connection efficiency of various browsers.
which browser is faster:
we can see that all JS string connection operations are optimized in browsers except IE. So when doing a lot of string connection operations in IE, you should consider performance issues.