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 = { /*...*/ };).