Develop Reference

Intercept a function in javascript

Following is my javaScript code.
var myObjfn = {
before : function(){
console.log("before");
},
loadA: function(){
console.log("loadA");
},
loadB: function(){
console.log("loadB");
},
loadC: function(){
console.log("loadC");
}
}
Whenever I call myObjfn.loadA(), it should call myObjfn.before() method before executing loadA method. Same for loadB() & loadC(). I don't want to explicitly call before() method in all loadA,loadB and loadC methods. Is there any option to achive this in javascript ?

You could do something like this. Which creates a wrapper function for each function in the object except the before function.
var myObjfn = { ... };
Object.keys(myObjfn).forEach(key => {
if (key === "before") return;
var oldFunc = myObjfn[key];
myObjfn[key] = function() {
myObjfn.before();
return oldFunc.apply(this, arguments);
};
});
myObjfn.loadA();
// "before"
// "loadA"

How to implement sub function in JavaScript

How can I implement sub functions in JavaScript
callMethod(); // Works
callMethod.doThisWay(); // Still works

Sure you can :-)
Just write
const callMethod = function () {
// ...
};
callMethod.doThisWay = function () {
// ...
};
and you're done :-)

This also works:
var callMethod = function() {
this.doThisWay = function () {
alert('doThisWay');
}
alert('callMethod');
return this;
};
var a = new callMethod();
a.doThisWay();
there is some other ways to do this also.

using revealling moduler pattern for complex in javascript

I have a very complex class so i decided to break into sub modules and trying to use revealing modules pattern.
I have main class and decided to divide into smaller container function. but in current scenario
But i am not able to access any internal function from outside i.e callSearchResultWithCallBack using searchFinder.Search.callSearchResultWithCallBack(). which pattern should i use to keep this code clean as well have control to call internal function in sub module.
Thanks
var searchFinder;
function SearchFinder() {
me = this;
this.searchResult = null;
this.init = function() {
declareControls();
createAccordian();
addEvents();
fillControls();
var declareControls = function() {
this.SearchButtons = jQuery('.doSearch');
this.InputLocation = jQuery('#inputLocation');
this.InputDistanceWithIn = jQuery('#inputDistanceWithIn');
this.InputName = jQuery('#inputName');
}
var addEvents = function() {
me.SearchButtons.click(function() {
me.Search();
});
}
var fillControls = function() {
var getGetCategory = function() {
}
}
}
this.Search = function() {
var url = '';
var searchCriteria = {};
validateAndCreateCriteria();
callSearchResultWithCallBack();
function validateAndCreateCriteria() {
function validateAandGetCategory() {
if (SearchValidation.ValidateZipCode(me.InputLocation.val().trim())) {
searchCriteria.location = me.InputLocation.val().trim();
} else if (SearchValidation.ValidateCityState(me.InputLocation.val().trim())) {
searchCriteria.location = me.InputLocation.val().trim();
}
}
}
// need to access it outsite
function callSearchResultWithCallBack() {
me.searchResult(searchCriteria, SearchResultCallBack);
function SearchResultCallBack() {
}
}
}
}
jQuery(function() {
searchFinder = new SearchFinder();
searchFinder.init();
searchFinder.Search.callSearchResultWithCallBack();
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>

This code has multiple issues, first I will address the fact that for example declareControls is not executing. First declare the function than execute!
this.init = function() {
var declareControls = function() {
this.SearchButtons = jQuery('.doSearch');
this.InputLocation = jQuery('#inputLocation');
this.InputDistanceWithIn = jQuery('#inputDistanceWithIn');
this.InputName = jQuery('#inputName');
}
var addEvents = function() {
this.SearchButtons.click(function() {
me.Search();
});
}
var fillControls = function() {
var getGetCategory = function() {
}
}
declareControls();
//createAccordian(); //not defined
addEvents();
fillControls();
}
Now let's look at others problems that will arise.
the me object referring to this is in the scope of searchFinder and does not refer to the same this in the instance of searchFinder.
function jQuery can be replaced by the commonly used $.
searchFinder.Search.callSearchResultWithCallBack() this is never going to work. Since the Search function is an object and callSearchResultWithCallBack isn't a property of this function.
Solution; make it part of the prototype of Search.
Steps:
Move callSearchResultWithCallBack outside the search function.
Add prototype to Search function
Call function via prototype.
function callSearchResultWithCallBack() {
me.searchResult(searchCriteria, SearchResultCallBack);
function SearchResultCallBack() {
}
}
this.Search.prototype.callSearchResultWithCallBack = callSearchResultWithCallBack;
If you want to fire this function outside of search use this:
searchFinder.Search.prototype.callSearchResultWithCallBack();
Please remember that callSearchResultWithCallBack will throw an error because searchCriteria is undefined.
This fixes your problems for now, but this code has to be revised thoroughly. But this should get you started. http://ejohn.org/blog/simple-javascript-inheritance/

Javascript concatenate a function similar to how text can be added

In javscript we can do this
var text = "the original text";
text+=";Add this on";
If a library has a function already defined (e.g)
//In the js library
library.somefunction = function() {...};
Is there a way to add something on so that I can have two functions run?
var myfunction = function() {...};
Something like:
library.somefunction += myfunction
So that both myfunction() and the original library.somefunction() are both run?

You can use this kind of code (leave scope empty to use default scope):
var createSequence = function(originalFn, newFn, scope) {
if (!newFn) {
return originalFn;
}
else {
return function() {
var result = originalFn.apply(scope || this, arguments);
newFn.apply(scope || this, arguments);
return result;
};
}
}
Then:
var sequence = createSequence(library.somefunction, myFunction);

I think what you want to create is a Hook (function) - you want to call library.somefunction but add a bit of your own code to run before. If that's the case, you can make your myfunction either call or return the library function after it's done with your bit of code.
var myfunction = function() {
// your code
// ...
return library.somefunction();
}

JavaScript call variable as Object and Function like jQuery

I'm trying to create a library for mobile and I want to be able to call the object as function and object like jquery does.
Example:
var test = function(elm) {
this.ajax = function(opt) { ... }
if ( elm ) {
var elms = document.querySelectorAll(elm);
}
}
and I want to be able to call it like this:
test("#id");
and like this:
test.ajax(opts);
LE:
Thank you guys for your fast responses!

In JavaScript, a function is actually just an object with code attached.
So instead of a plain object:
var test = {};
test.ajax = function() { /* ajax */ };
... use a function:
var test = function() { /* test */ };
test.ajax = function() { /* ajax */ };
In both cases, you can access test.ajax. The extra thing with the function is that you can call test.

Or mabye something like this:
Object.prototype.Test = function( method ) {
var method = method || null;
var elms = null;
/* Methods */
this.ajax = function(opt){
console.log('You called ajax method with options:');
console.log(opt);
}
/* Logic */
if (method in this) this[method].apply( this, Array.prototype.slice.call( arguments, 1 ));
else {
try {
elms = document.querySelectorAll(method);
}
catch(e) {
console.log(e.message);
}
}
}
window.onload = function() {
Test('ajax', {'url':'testurl.com'});
Test('#aid');
}