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Source:
Http://www.jb51.net/article/56504.htm
I. Commands to display information
The code is as follows:
<!DOCTYPE HTML><HTML><Head><title>Common Console Commands</title><Metahttp-equiv= "Content-type"content= "text/html; charset=utf-8" /></Head><Body><Scripttype= "Text/javascript">Console.log ('Hello'); Console.info ('Information'); Console.error ('Error'); Console.warn ('Warning');</Script></Body></HTML>
The most common is the console.log.
Two: Placeholder
Console The above concentration supports printf placeholder format, supported placeholders are: characters (%s), integers (%d or%i), floating-point numbers (%f), and objects (%o)
<script type= "Text/javascript" >console.log ("%d years%d months%d days", 2011,3,26); </script>Effect:
Iii. Grouping of information
The code is as follows:
<!DOCTYPE HTML><HTML><Head><title>Common Console Commands</title><Metahttp-equiv= "Content-type"content= "text/html; charset=utf-8" /></Head><Body><Scripttype= "Text/javascript">Console.group ("first set of information"); Console.log ("First set of first: my XX (http://www.jb51.net)"); Console.log ("The First group second article: XXX (http://jb51.net)"); Console.groupend (); Console.group ("Second set of information"); Console.log ("The second group first article: Program Enthusiasts QQ Group: 80535344"); Console.log ("Second group, article two: Welcome to join"); Console.groupend ();</Script></Body></HTML>
Effect:
Iv. Viewing the information of an object
Console.dir () can display all properties and methods of an object.
The code is as follows:
<script type= "Text/javascript" >var info = {blog:"http://www.jb51.net", Qqgroup: 80535344, message:"program enthusiasts welcome you to join"};console.dir (info); </script>Effect:
V. Display the contents of a node
Console.dirxml () is used to display the Html/xml code contained in a node of a Web page.
<!DOCTYPE HTML><HTML><Head><title>Common Console Commands</title><Metahttp-equiv= "Content-type"content= "text/html; charset=utf-8" /></Head><Body><DivID= "Info"><H3>My blog: www.ido321.com</H3><P>Program enthusiasts: 259280570, you are welcome to join</P></Div><Scripttype= "Text/javascript">varInfo=document.getElementById ('Info'); Console.dirxml (info);</Script></Body></HTML>
Effect:
Vi. Judging if the variable is true
Console.assert () is used to determine whether an expression or variable is true. If the result is no, a corresponding message is output in the console and an exception is thrown.
<script type= "Text/javascript" > var result = 1; Console.assert (result); var year = == 2018 ); </script>
1 is a value of 0, is true, and the second is false, displaying an error message on the console
Tracing the call trajectory of the function.
Console.trace () is used to track the call path of a function.
<script type= "Text/javascript" >/* How the function is called, in which the Console.trace () method is added to */ function add (A, b) {console.trace (); return a+B; var x = add3 (1,1 function add3 (A, b) {return Add2 (A, b);} function Add2 (A, b) {return Add1 (A, b);} function add1 (A, b) {return add (a, b);} </script> Console output Information:
Eight, chronograph function
Console.time () and Console.timeend () are used to display the elapsed time of the code.
<script type= "Text/javascript" > console.time ("console timer one"); for (var i=0;i<1000;i++) { for (var j=0;j<1000;j++) {}} Console.timeend ("console timer one"); </script>Run Time is 38.84ms
Performance analysis of Console.profile ()
Performance analysis (Profiler) is the analysis of the various parts of the running time, to find out the bottleneck, the method used is Console.profile ().
<script type= "Text/javascript" >functionAll () {alert (11); for(vari=0;i<10;i++) {Funca (1000);} FUNCB (10000); }functionFunca (count) { for(vari=0;i<count;i++) {}}functionFUNCB (count) { for(vari=0;i<count;i++) {}} console.profile (' Performance Analyzer '); All (); Console.profileend ();</script>
Description, LZ test, in all () without alert, control bar no output, plus, there is a performance analysis table, temporarily unclear why, if you know, you can comment.
JS Debug Tool Console command
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