If there is an output in the chrome/safari webkit inspector containing an object that prints out such as:
Only much more complicated with loads of nested objects (which is why a copy/paste wont do)
Is there a way to put this in a variable to inspect in further and process it after its been printed on the console (its printed via console.log), just only after its already in the console?
$_ will give you last output of console. So in console you can assign in to a variable.
Note that you can do this only in console and not from your own code.
Here's a way to do it without wrapping console.log in a custom log function:
var justLogged;
var oldLog = console.log;
console.log = function () {
oldLog.apply(console, arguments);
justLogged = arguments;
};
console.log('test');
// if necessary, restore console.log to its original behavior when you're finished with it
console.log = oldLog;
The value of justLogged will be ['test'], since you just logged it.
If you're looking to get the last output, do as Mohsen suggests.
If you're trying to get the last output of console.log, your best bet is a wrapper function. This can (1) do what you want (2) easily be disabled in production, which is helpful on old IE and hides debug messages.
var log = (function() {
var lastOutput;
var fn = function() {
lastOutput = arguments[0]; // save the last argument
console.log.apply(console, arguments); // defer to console.log
};
fn.last = function() {
return lastOutput;
};
return fn;
})();
log("abc123");
log.last(); // => "abc123"
Related
I've tried searching it up with multiple different wordings and on multiple websites with no answer, is it possible, is it not, and if so, how? I need to be able to get code to run when anythign is logged to the console and get what that thing was.
You can override console.log's default behavior:
var log = console.log;
var logs = []
console.log = function(e) {
log.apply(console, [].slice.call(arguments));
logs.push(e) //custom code
};
console.log("Hello World!")
console.log('Printed logs:', logs)
Save the original console
var log = console.log;
Monkey patch it i.e. modify it when run and all at runtime
//use the log instance and 'apply()' method to apply to inherit it
//we pass in a date for each call of console.log() when using the original ( log() )
log.apply(console, [(new Date().toString())].concat([].slice.call(arguments)) ); };
Now everytime we call - log() - we are calling the original
//to test it do this
log('test','this is the original console.log());
This is the patched version
console.log("This is the Monkey Patched console.log()!", "More text...");
I have an application that changes window.console.log to a function.
I want to reset window.console.log back it normal on a certain page, however when I run delete window.console.log; and call console.log('asd'); I get an exception
TypeError: console.log is not a function. (In 'console.log(error)', 'console.log' is undefined)
How do I restore it properly so a certain page can simply console.log normally instead of the custom one I had?
If you're able to access the code from before the application modifies console.log you could do the following:
window.defaultConsoleLog = console.log;
// here would be the code where the application modifies console.log
// calling console.log would now be the modified version from the application:
console.log('Hello');
// calling defaultConsoleLog would now call the original console.log:
defaultConsoleLog.log('Hello');
// OR
window.defaultConsoleLog('Hello');
// you can then reset to the original console.log like this:
console.log = window.defaultConsoleLog;
When you were doing delete window.console.log, this removes the function from the window.console object instead of resetting it.
You can simply store the old native function in an other variable or property and restore it later. For example :
// Storing the native console.log into a property in window
window.oldLog = window.console.log
// Overriding the console.log function
console.log = (str) => { document.getElementById('logs').textContent += str }
console.log('Calling the new console.log')
window.oldLog('Calling the old console.log')
// Now resetting the native console.log
console.log = window.oldLog
// Clearing up
delete window.oldLog
console.log('Calling the restored console.log')
<pre id="logs"></pre>
I've been hunting around Google and various JavaScript websites, but I've yet to find an answer for this. Is there any way that I could use JavaScript/JQuery to monitor events such as console.log()?
For example, I'd like to trigger an even when a separate, cumbersome-to-deal with script calls console.log('foo'); When using any web inspector with a JavaScript console, it's easy to see foo pop up when the script logs it, but is there a way I can hook that event with a different script?
Code borrowed from Can I extend the console object (for rerouting the logging) in javascript?:
(function() {
var exLog = console.log;
console.log = function(msg) {
exLog.apply(console, arguments);
alert(msg);
}
})()
This should allow you to do just about anything when console.log() has been executed, as long as this code runs before console.log() is executed.
While you cannot extend console, you can wrap each of it's methods. The code below intercepts every logging method and records each call in a variable called log.
var actualConsole = window.console;
var c = window.console = {};
var log={};
for (var m in actualConsole){
if (typeof console[m] ==='object'){
c[m]=console[m];
}else if (typeof actualConsole[m] ==='function'){
c[m]=function () {
var args = Array.prototype.slice.call(arguments);
log[this]=log[this]||[];
log[this].push(args);
actualConsole[this].apply(actualConsole,args);
}.bind(m);
}// else - nothing else expected
}
console.log('log',1);
console.log('log',2);
console.error('error',1);
console.warn('warn',1);
actualConsole.log('log:',log);
Log looks like:
{"log":[["log",1],["log",2]],"error":[["error",1]],"warn":[["warn",1]]}
I'm trying to get the console.log as string in pure JavaScript.
My input is a script, which I'm not familiar with, and I want to collect all the messages in the console.log into a string.
For example:
function doSomething(){
console.log("start");
console.log("end");
var consoleLog = getConsoleLog();
return consoleLog;
}
function getConsoleLog(){
// How to implement this?
}
alert(doSomething());
JSFiddle link
Note that I do not need to alert the log - this is just a simple example of testing the functionality. I'll have to do some operations on the log's content.
You could overwrite console.log method before using it:
var logBackup = console.log;
var logMessages = [];
console.log = function() {
logMessages.push.apply(logMessages, arguments);
logBackup.apply(console, arguments);
};
Using apply and arguments preserves the correct console.log behaviour, i.e. you can add multiple log messages with a single call.
It will push all new console.log messages to logMessages array.
for security issues, there is no api to read the history of console.log().
If I receive an error from a framework or an error from the browser. Basically a runtime error of any kind. Without modifying the framework, is it possible for me to override the console logs that these frameworks make and the browser's errors. I want to use my own framework with own error handling system when informing the user of errors of practically anything runtime (not syntax errors). I don't know if you would class it all as runtime errors because of the way javascript is executed in the browser but hopefully you will get me?
Is this possible if all the frameworks are written in Javascript?
How is this achieved?
What considerations do I have to make between different browsers?
Thanks
You are probably looking for a try-catch block:
try {
alert(foo);
} catch(e) {
alert('The code got the following error: '+e.message);
}
Whenever the code between the try {} receives an error, the catch(e) {} block will execute, with the argument e being the error object for the error that occurred. In this case, the variable foo is not defined, so executing this code will result in an alert message saying "The code got the following error: foo is not defined"
While not over-riding console.log, you may be achieve the same effect by overriding window.onerror.
From the MDN documentation
window.onerror = function myErrorHandler(errorMsg, url, lineNumber) {
// Log the error here -- perhaps using an AJAX call
}
You could try overriding the console.log() function.
//Save original reference
var originalConsole = console;
//Override
console = {};
console.log = function()
{
//According to MDN the console.log function can receive a variable number of params
for(var i=0; i<arguments.length; i++)
{
//Make your changes here, then call the original console.log function
originalConsole.log("Change something: "+arguments[i]);
}
//Or maybe do something here after parsing all the arguments
//...
}
console.log("one", "two");
JSFiddle here.
You can override the console logs by creating a "console" object and overriding it's .log() function:
var console = {};
console.log = function(){};
Some browsers require this to be added to the window object directly; so, for browser compatibility, also add:
window.console = console;
Additionally, you can override other console functions (e.g. console.info, console.warn and console.error) if you're using those too.
Also, consider reading this blog post from Udi Talias on overriding the console functions. Good and quick read!
You can custom your console.log here
// copy the original
let originalConsole = Object.assign({}, console);
// do something with your log.
console.log = (value) => {
//some cool condition
if (true) {
value = "new_log : " + value
}
originalConsole.log(value);
};