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JS Debug Tool Console command

Source: Internet
Author: User
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It was not known that the console was so powerful that it was able to count time and analyze performance bottlenecks.

Original link: http://www.jb51.net/article/56504.htm

I. Commands to display information

Copy CodeThe code is as follows:
<! DOCTYPE html>
<title> Common Console Commands </title>
<meta http-equiv= "Content-type" content= "text/html; Charset=utf-8 "/>
<body>
<script type= "Text/javascript" >
Console.log (' Hello ');
Console.info (' information ');
Console.error (' error ');
Console.warn (' warning ');
</script>
</body>

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)

Copy CodeThe code is as follows:
<script type= "Text/javascript" >
Console.log ("%d years%d months%d days", 2011,3,26);
</script>


Effect:

Iii. Grouping of information

Copy CodeThe code is as follows:
<! DOCTYPE html>
<title> Common Console Commands </title>
<meta http-equiv= "Content-type" content= "text/html; Charset=utf-8 "/>
<body>
<script type= "Text/javascript" >
Console.group ("First set of Information");

Console.log ("First Group first: my XX (http://www.jb51.net)");

Console.log ("First Group II: XXX (http://jb51.net)");

Console.groupend ();

Console.group ("Second set of Information");

Console.log ("The second group first: program Enthusiasts QQ Group: 80535344");

Console.log ("Second group II: welcome you to join");

Console.groupend ();
</script>
</body>

Effect:

Iv. Viewing the information of an object

Console.dir () can display all properties and methods of an object.

Copy CodeThe 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.

Copy CodeThe code is as follows:
<! DOCTYPE html>
<title> Common Console Commands </title>
<meta http-equiv= "Content-type" content= "text/html; Charset=utf-8 "/>
<body>
<div id= "Info" >
<p> Program Enthusiasts: 259280570, you are welcome to join </p>
</div>
<script type= "Text/javascript" >
var info = document.getElementById (' info ');
Console.dirxml (info);
</script>
</body>

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.

Copy CodeThe code is as follows:
<script type= "Text/javascript" >
var result = 1;
Console.assert (result);
var year = 2014;
Console.assert (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.

Copy CodeThe code is as follows:
<script type= "Text/javascript" >
/* How the function is called, in which the Console.trace () method is available */
function Add (A, b) {
Console.trace ();
return a+b;
}
var x = ADD3 (n);
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.

Copy CodeThe code is as follows:
<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 ().

Copy CodeThe code is as follows:
<script type= "Text/javascript" >
function All () {
Alert (11);
for (Var i=0;i<10;i++) {
Funca (1000);
}
FUNCB (10000);
}

function Funca (count) {
for (Var i=0;i<count;i++) {}
}

function FUNCB (count) {
for (Var i=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

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

Related Keywords:
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