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Calling a function within a function from outside [closed]

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I am having some trouble here trying to call function C from an onClick event on the page.
function leftArrowClicked() {
functionA(functionC);
}
function functionA() {
function functionB(w) {
function functionC() {
// do stuff
};
}
}
<div id="dashboard_left_arrow" onclick="leftArrowClicked()">Click</div>
But it's of course not working. Currently seeing 'functionC is not defined' in the console. I don't know much about nested functions, hence probably why my method isn't working. Any ideas?

You can use something called Modular Design Patterns. It goes something like this -- you can see that functionA is an function that is already invoked, so I can call functionB directly on that because it is returned inside an object. Calling functionC can be done on top of that.
var functionA = (function() {
function functionB(w) {
function functionC() {
// do stuff
return 'inside functionC';
}
return {functionC:functionC};
}
return {functionB:functionB};
})();
function leftArrowClicked() {
console.log(functionA.functionB('').functionC());
}
<div id="dashboard_left_arrow" onclick="leftArrowClicked()">Click</div>

Jquery object function waits for all the statement to complete [closed]

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As I am learning a jquery and new to it I created a jquery object like
$(function () {a();b();c()})
As I have 3 method call under the Jquery object function and the Jquery function waits for end of every method call after that only displays the result . So I wanted to know is there a way that we can show work information of those methods which has completed the work , like if a() has been called and work is done it should display the result and should not wait for other methods to to be called and processed .

There are multiple ways to handle async functions in JavaScript. The easiest way is using callbacks if you are new to this language.
function a(callbackA) {
// do something...
console.log('A')
callbackA();
}
function b(callbackB) {
// do something...
console.log('B')
callbackB();
}
function c() {
// do something...
console.log('C')
}
// usage:
a(function() {
b(function() {
c();
});
});

How does this javascript class and method work? [duplicate]

This question already has answers here:
Where do the parameters in a javascript callback function come from?
(3 answers)
Closed 4 years ago.
As seen here from Twilio's documentation, how does the following code work? We have a connection class and an on method. If I haven't previously defined what hasEarlyMedia, showRingingIndicator, or playOutgoingRinging mean, then how does the on method know what they mean and what to do with them? Thanks.
connection.on('ringing', function(hasEarlyMedia) {
showRingingIndicator();
if (hasEarlyMedia) { playOutgoingRinging(); }
});

Maybe is easier to understand if we rewrite the code like this:
// when the Connection has entered the ringing state,
// call handleRingingEvent (callback function) and pass an argument,
// a boolean denoting whether there is early media available from the callee
connection.on('ringing', handleRingingEvent);
function handleRingingEvent(hasEarlyMedia) {
showRingingIndicator();
if (hasEarlyMedia) {
playOutgoingRinging();
}
}
// if not defined somewhere else
function showRingingIndicator() {
// do something
}
// if not defined somewhere else
function playOutgoingRinging() {
// do something
}
I hope this helps.

hasEarlyMedia is an argument. Please check
showRingingIndicator(); and playOutgoingRinging(); method must be defined somewhere. Must be function declared in your one of the library which you have included in your file.

Call a function inside DOM ready [closed]

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I Have a Javascript library and unfortunately i Shouldn't change it .
there is a DOM Ready function and i need to call a function inside it, codes as below:
function ready(fn){
if (document.readyState != 'loading'){
console.log('fn called');
fn();
}
else {
console.log('fn loaded');
document.addEventListener('DOMContentLoaded', fn);
}
}
ready(function(){
function hello() {
console.log("hello world!");
}
});
then i need to call hello from outside of this scope, from another function like this:
function btnstart(){
hello();
}
how i can do this?

This is an explanation of your problem in a bit more detail. It's not an answer and I don't expect it to be accepted. It's to help you understand why you can't do what you're asking, unless you can change the existing code.
The problem you are facing is that you create an anonymous function that contains hello() and then pass that to another function. Outside the scope of that anonymous function, hello() does not exist and is therefore not accessible.
Take this example...
function domReady(fn) {
fn.hello();
}
domReady(function() {
function hello() {
console.log("hello");
}
});
This creates an anonymous function and passes it to domReady(), which in turn references it as fn. However, this will also fail as fn does not have a function called hello(). That method would be created if you called fn(), but would still only exist inside that function.
What you really need to do is move hello() outside the scope of domReady() and just pass it as a reference, like this...
function domReady(fn) {
fn();
}
function hello() {
console.log("hello");
}
domReady(hello); // note there are no parenthesis () after hello, so it is a reference and not immediate executed
If you can change that then you can simply call hello() whenever you like (within the same scope). If you cannot change that then you cannot do what you are asking.

Should favor "_this" instead of "self" in javascript? [closed]

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In Airbnb JavaScript Style Guide, they mentioned "When saving a reference to this use _this."
// bad
function() {
var self = this;
return function() {
console.log(self);
};
}
// bad
function() {
var that = this;
return function() {
console.log(that);
};
}
// good
function() {
var _this = this;
return function() {
console.log(_this);
};
}
However, I read few books mentioned "self" is good. Like in AngularJS: Up and Running.
<script type="text/javascript">
angular.module('notesApp', []).controller('MainCtrl', [function () {
var self = this;
self.message = 'Hello ';
self.changeMessage = function () {
self.message = 'Goodbye';
};
}]);
</script>
So, could any one tell me the reason to use "_this" instead of "self"?

This is just personal preference. However, it's best to only use one option inside a project's codebase. So don't use _this in one function block, then that or self in the other..

As noted by others, this is purely a coding style preference. I would offer a suggestion: If your team's code base is interested in continuing to use lexical scoping for this, then consider using ES6's fat arrow function instead to avoid creating an unnecessary variable.
This of course all depends if your project is ready to implement ES6 features.

I would not use self as it is already in use as another pointer to the window object. See here (part way down page) for an example of using self like a variable (without needing to prefix it as window.self): https://developer.mozilla.org/en/docs/Web/API/Window/self