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I. Commands to display information
1 <!DOCTYPE HTML>2 <HTML>3 <Head>4 <title>Common Console Commands</title>5 <Metahttp-equiv= "Content-type"content= "text/html; charset=utf-8" />6 </Head>7 <Body>8 <Scripttype= "Text/javascript">9 Console.log ('Hello');Ten Console.info ('Information'); One Console.error ('Error'); A Console.warn ('Warning'); - </Script> - </Body> the </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)
1 <script type= "Text/javascript" >2 console.log ("%d years%d months%d days", 2011,3,26); 3 </script>Effect:
Iii. Grouping of information
1 <!DOCTYPE HTML>2 <HTML>3 <Head>4 <title>Common Console Commands</title>5 <Metahttp-equiv= "Content-type"content= "text/html; charset=utf-8" />6 </Head>7 <Body>8 <Scripttype= "Text/javascript">9 Console.group ("first set of information");Ten One Console.log ("First set of first: my blog (http://www.ido321.com)"); A - Console.log ("First group Second article: CSDN (http://blog.csdn.net/u011043843)"); - the console.groupend (); - - Console.group ("Second set of information"); - + Console.log ("The second group first article: Program Enthusiasts QQ Group: 259280570"); - + Console.log ("Second group, article two: Welcome to join"); A at console.groupend (); - </Script> - </Body> - </HTML>
Effect:
Iv. Viewing the information of an object
Console.dir () can display all properties and methods of an object.
1 <script type= "Text/javascript" >2 varinfo = {3 Blog: "/http// Www.ido321.com ",4 qqgroup:259280570,5 message:" Program enthusiasts welcome you to join " 6 }; 7 Console.dir (info); 8 </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.
1 <!DOCTYPE HTML>2 <HTML>3 <Head>4 <title>Common Console Commands</title>5 <Metahttp-equiv= "Content-type"content= "text/html; charset=utf-8" />6 </Head>7 <Body>8 <DivID= "Info">9 <H3>My blog: www.ido321.com</H3>Ten <P>Program enthusiasts: 259280570, you are welcome to join</P> One </Div> A <Scripttype= "Text/javascript"> - Varinfo=document.getElementById ('Info'); - Console.dirxml (info); the </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.
1 <script type= "Text/javascript" >2 varresult = 1; 3 Console.assert (result); 4 Varyear =; 5 Console.assert (Year = = 2018); 6 </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.
1<script type= "Text/javascript" >2 /*How the function is called, in which the Console.trace () method is added to the*/3 Functionadd (A, b) {4 console.trace ();5returna+b;6 }7Varx = ADD3 ();8 Functionadd3 (A, b) {returnadd2 (A, b);}9 Functionadd2 (A, b) {returnadd1 (A, b);}Ten Functionadd1 (A, b) {Returnadd (A, b);} One</script>
Console output Information:
Eight, chronograph function
Console.time () and Console.timeend () are used to display the elapsed time of the code.
1 <script type= "Text/javascript" >2 console.time ("console timer one"); 3 for (vari=0;i<1000;i++) {4 for (varj=0;j<1000;j++) {} 5 }6 console.timeend ("console timer one"); 7 </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 ().
1<script type= "Text/javascript" >2 Functionall () {3Alert (11);4 for(vari=0;i<10;i++){5Funca (1000);6 }7FUNCB (10000);8 }9 Ten Functionfunca (count) { One for(vari=0;i<count;i++){} A } - - FUNCTIONFUNCB (count) { the for(vari=0;i<count;i++){} - } - -Console.profile (' Performance Analyzer ')); + All (); - console.profileend (); +</script>
Output
Nine console commands to make JS debugging easier
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