I've been trying to make custom console commands with JavaScript with no success. There seem to be no sources about my question.
When I say "JavaScript Console Commands" I mean I'd like to make my own commands from the console. For example, if the visitor types "custom.command()" in my website's console area, I want the output to be: console.log("This is my custom command");.
You don't have to do anything special; just create an object at global scope with functions on it, and the user will be able to use it from the devtools console.
For instance (in a script, not a module):
const custom = {
command() {
console.log("This is my custom command.");
},
};
Because that's at global scope, it creates a global, and so it is accessible in the console when your page is open.
(It doesn't have to be an object; you could just create a function at global scope, but your example usage was using an object.)
If you wanted to do this from a module, since the top level of a module isn't global scope, you'd have to do the same kind of thing you have to do to create a global in a function, which is covered by the answers to this question (in your case, it' basically assign to a property on window: window.custom = { /*...*/ };).
I am trying to implement the following answer from another question:
https://stackoverflow.com/a/26469105/2402594
Basically I need to add an extra check to a jQuery function. The following code is in jQuery library:
But I can't modify the original jQuery, so I am creating a patch in a separate file. What I am doing is overriding the find function and add functionality as follows:
(function() {
var originalFind = jQuery.fn.find;
jQuery.fn.find = function () {
try {
document === document;
}
catch (err) {
document = window.document;
}
return originalFind.apply(this, arguments);
};
})();
The function is overridden correctly, however, when the code calls 'find', my 'try' doesn't throw any exception when it should because the scope is different than the one inside the Sizzle function, so the original issue is still there.
I have also tried duplicating all of the Sizzle code, adding my modification and assigning it to jQuery.fn.find as done above, however the scope issue is still there and some crashes happen.
I need 'document' to be set before it reaches the following check or it crashes due to permission denied:
How could I share the scope so that the try/catch can be done correctly? Is it even possible? Any other ideas?
Thank you
As we all known, JavaScript has function scope: Each function creates a new scope. Scope determines the accessibility (visibility) of these variables. Variables defined inside a function are not accessible (visible) from outside the function.
So, if the document is defined in the JQuery library function, I think you can't access it. You could try to define a global variable to store the document, then, you can access it in the JQuery library function and the override function.
More details about Javascript Scope, check these links: link1 and link2
Lets say I have one variable var car = 'VW' in index.html
index.html is the binding of my application, from there I access several modules:
<script>
var car = 'VW';
var Initializer = require('./js/initializer');
Initializer.check_requirements();
</script>
Now in initializer I try to access this variable what does not work.
var Initializer = {
check_requirements: function(){console.log(car)};
};
module.exports = Initializer;
However when I attach the variable car to window:
window.car = 'VW';
Then Im able to access it in my module over window.car;
How do I create an global variable car that I can also access in my modules, so that I do not have to attach to window?
Thanks
In a browser context, a "global" variable is in fact a property of the window object, which acts as the global context. The syntax you have in your question, a bare var statement in a script tag in an HTML page, will in fact add that var name as a property to the window. However, since you're using what looks like a CommonJS require statement here, which is not natively supported in most browsers, there's probably a compile step you're not including in your question that's preventing this from working the way you expect.
However, the short answer is, don't do this if you can avoid it. Most applications of global variables are better accomplished with parameters, e.g. Initializer.check_requirements(car);, or in a separate module storing configuration settings, or other approaches.
Is it possible to sandbox javascript module from DOM manipulation? Fo example
var Core = {
register: function(config){config.init()},
publicApi: {
msgbox: function(msg){alert(msg)}
}
}
Core.register({
name: 'testmodule',
init: function(){
/* from there i want to see only function defined in Core.publicApi, no jQuery direct access, no DOM */
}
});
Well, somewhat: you can sandbox the function, but its callees will also be sandboxed. That means even stuff in Core.publicApi won't be able to access document and the like. Or, at least, there's no bulletproof sandboxing in Javascript that will allow that bridging.
You can cripple what's available by temporarily overwriting the window variable:
var window = {"Core": Core};
But then no global variable (even such as alert) will exist for the callees. This will most likely break your API.
You can add another member (like _unsandboxed or whatever) into the new window variable to allow your API to access the members. But, as I said, it's not bulletproof since sandboxed functions can still access _unsandboxed.
I thought I'd found the solution a while ago (see my blog):
If you ever get the JavaScript (or should that be JScript) error "Can't execute code from a freed script" - try moving any meta tags in the head so that they're before your script tags.
...but based on one of the most recent blog comments, the fix I suggested may not work for everyone. I thought this would be a good one to open up to the StackOverflow community....
What causes the error "Can't execute code from a freed script" and what are the solutions/workarounds?
You get this error when you call a function that was created in a window or frame that no longer exists.
If you don't know in advance if the window still exists, you can do a try/catch to detect it:
try
{
f();
}
catch(e)
{
if (e.number == -2146823277)
// f is no longer available
...
}
The error is caused when the 'parent' window of script is disposed (ie: closed) but a reference to the script which is still held (such as in another window) is invoked. Even though the 'object' is still alive, the context in which it wants to execute is not.
It's somewhat dirty, but it works for my Windows Sidebar Gadget:
Here is the general idea:
The 'main' window sets up a function which will eval'uate some code, yup, it's that ugly.
Then a 'child' can call this "builder function" (which is /bound to the scope of the main window/) and get back a function which is also bound to the 'main' window. An obvious disadvantage is, of course, that the function being 'rebound' can't closure over the scope it is seemingly defined in... anyway, enough of the gibbering:
This is partially pseudo-code, but I use a variant of it on a Windows Sidebar Gadget (I keep saying this because Sidebar Gadgets run in "unrestricted zone 0", which may -- or may not -- change the scenario greatly.)
// This has to be setup from the main window, not a child/etc!
mainWindow.functionBuilder = function (func, args) {
// trim the name, if any
var funcStr = ("" + func).replace(/^function\s+[^\s(]+\s*\(/, "function (")
try {
var rebuilt
eval("rebuilt = (" + funcStr + ")")
return rebuilt(args)
} catch (e) {
alert("oops! " + e.message)
}
}
// then in the child, as an example
// as stated above, even though function (args) looks like it's
// a closure in the child scope, IT IS NOT. There you go :)
var x = {blerg: 2}
functionInMainWindowContenxt = mainWindow.functionBuilder(function (args) {
// in here args is in the bound scope -- have at the child objects! :-/
function fn (blah) {
return blah * args.blerg
}
return fn
}, x)
x.blerg = 7
functionInMainWindowContext(6) // -> 42 if I did my math right
As a variant, the main window should be able to pass the functionBuilder function to the child window -- as long as the functionBuilder function is defined in the main window context!
I feel like I used too many words. YMMV.
Here's a very specific case in which I've seen this behavior. It is reproducible for me in IE6 and IE7.
From within an iframe:
window.parent.mySpecialHandler = function() { ...work... }
Then, after reloading the iframe with new content, in the window containing the iframe:
window.mySpecialHandler();
This call fails with "Can't execute code from a freed script" because mySpecialHandler was defined in a context (the iframe's original DOM) that no longer exits. (Reloading the iframe destroyed this context.)
You can however safely set "serializeable" values (primitives, object graphs that don't reference functions directly) in the parent window. If you really need a separate window (in my case, an iframe) to specify some work to a remote window, you can pass the work as a String and "eval" it in the receiver. Be careful with this, it generally doesn't make for a clean or secure implementation.
If you are trying to access the JS object, the easiest way is to create a copy:
var objectCopy = JSON.parse(JSON.stringify(object));
Hope it'll help.
This error can occur in MSIE when a child window tries to communicate with a parent window which is no longer open.
(Not exactly the most helpful error message text in the world.)
Beginning in IE9 we began receiving this error when calling .getTime() on a Date object stored in an Array within another Object. The solution was to make sure it was a Date before calling Date methods:
Fail: rowTime = wl.rowData[a][12].getTime()
Pass: rowTime = new Date(wl.rowData[a][12]).getTime()
I ran into this problem when inside of a child frame I added a reference type to the top level window and attempted to access it after the child window reloaded
i.e.
// set the value on first load
window.top.timestamp = new Date();
// after frame reloads, try to access the value
if(window.top.timestamp) // <--- Raises exception
...
I was able to resolve the issue by using only primitive types
// set the value on first load
window.top.timestamp = Number(new Date());
This isn't really an answer, but more an example of where this precisely happens.
We have frame A and frame B (this wasn't my idea, but I have to live with it). Frame A never changes, Frame B changes constantly. We cannot apply code changes directly into frame A, so (per the vendor's instructions) we can only run JavaScript in frame B - the exact frame that keeps changing.
We have a piece of JavaScript that needs to run every 5 seconds, so the JavaScript in frame B create a new script tag and inserts into into the head section of frame B. The setInterval exists in this new scripts (the one injected), as well as the function to invoke. Even though the injected JavaScript is technically loaded by frame A (since it now contains the script tag), once frame B changes, the function is no longer accessible by the setInterval.
I got this error in IE9 within a page that eventually opens an iFrame. As long as the iFrame wasn't open, I could use localStorage. Once the iFrame was opened and closed, I wasn't able to use the localStorage anymore because of this error. To fix it, I had to add this code to in the Javascript that was inside the iFrame and also using the localStorage.
if (window.parent) {
localStorage = window.parent.localStorage;
}
got this error in DHTMLX while opening a dialogue & parent id or current window id not found
$(document).ready(function () {
if (parent.dxWindowMngr == undefined) return;
DhtmlxJS.GetCurrentWindow('wnManageConDlg').show();
});
Just make sure you are sending correct curr/parent window id while opening a dialogue
On update of iframe's src i am getting that error.
Got that error by accessing an event(click in my case) of an element in the main window like this (calling the main/outmost window directly):
top.$("#settings").on("click",function(){
$("#settings_modal").modal("show");
});
I just changed it like this and it works fine (calling the parent of the parent of the iframe window):
$('#settings', window.parent.parent.document).on("click",function(){
$("#settings_modal").modal("show");
});
My iframe containing the modal is also inside another iframe.
The explanations are very relevant in the previous answers. Just trying to provide my scenario. Hope this can help others.
we were using:
<script> window.document.writeln(table) </script>
, and calling other functions in the script on onchange events but writeln completely overrides the HTML in IE where as it is having different behavior in chrome.
we changed it to:
<script> window.document.body.innerHTML = table;</script>
Thus retained the script which fixed the issue.