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<! DOCTYPE html><Html><Head><Title> Common Console commands</Title><Metahttp-equiv="Content-type"Content=</head> << Span class= "Hljs-name" >body> <script type= "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: PlaceholderConsole The above concentration supports printf placeholder format, supported placeholders are: characters (%s), integers (%d or%i), floating-point numbers (%f), and Objects (%o)
<type="Text/javascript" > console.log ("%d%d months%d days", 3, +); </script> Effect:
Iii. Grouping of information
<! 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 Group One: Welcome to my Blog"); Console.log ("First group II: Hello! "); Console.groupend (); Console.group ("Second set of Information"); Console.log ("second group first: Hello"); Console.log ("second group II: welcome you 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.
<type="Text/javascript" > var info = {blog:"http://www.ido321.com", Qqgroup: 259280570, message:Console.dir (info); </script> Effect:
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> Welcome to view my blog </ h3> <p> hope to communicate with each other </p> </ div> <script type= "Text/javascript" > var info = Span class= "hljs-built_in" >document.getelementbyid ( ' info '); console.dirxml (info); </script> </ body> </HTML>
Effect:
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.
<type="Text/javascript" > console.assert (1==2, "error");// Will error
</script>
1 equals 2, error errors, assert (assertion) is a good feature to ensure the correctness of the program.
Tracing the call trajectory of the function.Console.trace () is used to track the call path of a function.
<ScriptType="Text/javascript" > /* How the function is called, in which the Console.trace () method is available */functionadd (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 (b);} </SCRIPT>
Console output Information:
Console.time () and Console.timeend () are used to display the elapsed time of the code.
<type="Text/javascript" >console.time ("console timer one"); For (var i=0;i<1000;i++) {for (var j=0;j<1000;j++) {}} Console.timee nd ("console timer one"); </script> Run Time is 15.947ms
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 ().
<ScriptType="Text/javascript" > functionAll () {alert (11);Forvar 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>
Output
9 Console commands to make JavaScript easier to debug
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