I. Commands to display information
Console.log (' hello '); Console.info (' information '); Console.error (' error '); Console.warn (' warning ');
Second, 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)
Console.log ("%d years%d months%d days", 2011,3,26);
Iii. Grouping of information
Console.group ("First set of Information"); Console.log ("first Group One"); Console.log ("first Group II"); Console.groupend (); Console.group ("Second set of Information") ; Console.log ("second group first"); Console.log ("second group, second article"); Console.groupend ();
Iv. Viewing the information of an object
Console.dir () can display all properties and methods of an object.
var info = { qq:"332877552", message:"hahaha", "ddddd" }; Console.dir (info);
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.
<div id= "Info" > var info = document.getElementById (' info '); Console.dirxml (info); </script>
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.
var result = 1; Console.assert (result); //1 non-0 value, true;var year = == 2018) ; //While the second judge is false, displays an error message on the console
Tracing the call path of the function
Console.trace () to track the call path of a function
Console.log (' Print information '); /* How the function is called, in which the Console.trace () method is added to the */ 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);}
Eight, chronograph function
Console.time () and Console.timeend () are used to display the elapsed time of the code.
Console.log (' Print information '); Console.time ("console timer one"); for (var i=0;i<100;i++) { for (var j=0;j<100;j++) {} } Console.timeend ("console timer one");
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 ().
function All () { alert (one); for (var i=0;i<10;i++) { Funca (+); } 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 ();
Nine Console commands to make JS debugging easier