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Passing values from an object inside a function

I have been working all day trying to pass the value of "returnData.salary" inside the "readData" function to
the object inside the "calculateTax" function which is suppose to take the salary value and calculate state and federal taxes. I am stumped, I can't find anything on the internet which provides a good example for me to work with. The examples are either way to simple or super complex. Any help would be appreciated.
I apologize in advance if I did not submit this question in the correct format. This is my first time asking for help on stackoverflow.
function readForm() {
var returnData = {};
returnData.name = $("#name").val();
returnData.lastName = $("#lastName").val();
returnData.age = $("#age").val();
returnData.gender = $("[name=gender]:checked").val();
returnData.salary = $("#salary").val();
returnData.isManager = $("#isManager").val();
returnData.myTextArea = $("#myTextArea").val();
$("#name2").text(returnData.name);
$("#lastName2").text(returnData.lastName);
$("#age2").text(returnData.age);
$("#gender2").text(returnData.gender);
$("#salary2").text(returnData.salary);
$("#myTextArea2").text(returnData.myTextArea);
if ($(isManager).is(':checked')) {
$("#isManager2").text("Yes");
}
else {
$("#isManager2").text("No");
}
//$("#employeeForm")[0].reset();
} //end of readForm function
function calculateTax() {
console.log("Button Works");
var calculateTax = {
state: function(num) {
num *= 0.09;
return num;
}
, federal: function(num) {
if (num > 10000) {
num *= 0.2;
return num;
}
else {
num * 0.1;
return num;
}
}
, exempt: true
};
}
//Invoke readForm function when the submit button is clicked.
$(document).ready(function () {
$("#btnSubmit").on("click", readForm);
$("#btnCalculate").on("click", calculateTax);
})
</script>

Well, simply put; you can't. Not like this anyway. Or, at least not pass the value to the function directly.
You are using global functions right now, which are not inside a class. If it was inside a class, you could instantiate the class and save it to this (which would be the class' instance). However, I'm assuming classes are a bit over complicated in this case. What you could do, is set variables globally so all functions can use them, like this;
//declare the global variable so it exists for every function
var returnData = {};
function readForm() {
//We do NOT redeclare the "var" again. It's global now.
returnData = {}; //Reset the global variable when this function is called
returnData.name = $("#name").val();
returnData.lastName = $("#lastName").val();
returnData.age = $("#age").val();
returnData.gender = $("[name=gender]:checked").val();
returnData.salary = $("#salary").val();
returnData.isManager = $("#isManager").val();
returnData.myTextArea = $("#myTextArea").val();
//Rest of your function
}
function calculateTax(){
console.log(returnData) //works here
}
Note that you do overwrite global variables, so it's best to reset them on every function call. You might get old data stuck in there, otherwise.

.map() unable to access Object's this.function

Thanks in advance for any responses:
I don't think this is a duplicate: I reviewed that article in the first comment, that is just a general breakdown of objects and using "this" within javascript.
My other this.function's perform just fine, so I at least have the basics of JS Obj's figured out.
This issue is related to using .map() with a this.function within a constructed object.
The following Google Appscript code uses .map() to update a string in a 2d array. [[string, int],[string, int]]
For some reason, when using .map() it is am unable to access the function "this.removeLeadingZero". If that same function is placed outside of the OBJ it can be called and everything works just fine. For some reason the system claims row[0] is an [object, Object] but when I typeof(row[0]) it returns "string" as it should.
Error: TypeError: Cannot find function removeLeadingZero in object [object Object]. (line 106, file "DEEP UPC MATCH")
Is there any issue using this.function's with .map() inside an object or am I using an incorrect syntax?
function test2DMapping(){
var tool = new WorkingMappingExample()
var boot = tool.arrayBuild();
Logger.log(boot)
}
function WorkingMappingExample(){
this.arr= [["01234", 100],["401234", 101],["012340", 13],["01234", 0422141],["01234", 2],["12340",3],["01234", 1],["01234", 2],["12340",3],["01234", 1],["01234", 2],["12340",3],["01234", 1],["01234", 2],["12340",3]];
//mapping appears faster that normal iterations
this.arrayBuild = function(){
var newArray1 =
this.arr.map( function( row ) {
**var mUPC = removeLeadingZero2(row[0])** //working
**var mUPC = this.removeLeadingZero(row[0])** // not working
var index = row[1]
Logger.log(mUPC + " " + index)
row = [mUPC, index]
return row
} )
return newArray1;
};
}; //end of OBJ
//THE NEXT 2 FUNCTIONS ARE WORKING OUTSIDE OF THE OBJECT
function removeLeadingZero2(upc){
try {
if (typeof(upc[0]) == "string"){
return upc.replace(/^0+/, '')
} else {
var stringer = upc.toString();
return stringer.replace(/^0+/, '')
}
} catch (err) {
Logger.log(err);
return upc;
}
}
function trimFirstTwoLastOne (upc) {
try {
return upc.substring(2, upc.length - 1); //takes off the first 2 #'s off and the last 1 #'s
} catch (err) {
Logger.log(err);
return upc;
}
}

Inside the function that you pass to map, this doesn't refer to what you think it does. The mapping function has its own this, which refers to window, normally:
var newArray1 = this.arr.map(function(row) {
// this === window
var mUPC = this.removeLeadingZero(row[0]);
var index = row[1];
Logger.log(mUPC + " " + index);
return [mUPC, index];
});
You have four options:
Array#map takes a thisArg which you can use to tell map what the this object in the function should be:
var newArray1 = this.arr.map(function(row) {
// this === (outer this)
var mUPC = this.removeLeadingZero(row[0]);
// ...
}, this); // pass a thisArg
Manually bind the function:
var newArray1 = this.arr.map(function(row) {
// this === (outer this)
var mUPC = this.removeLeadingZero(row[0]);
// ...
}.bind(this)); // bind the function to this
Store a reference to the outer this:
var self = this;
var newArray1 = this.arr.map(function(row) {
// self === (outer this)
var mUPC = self.removeLeadingZero(row[0]);
// ...
});
Use an arrow function:
var newArray1 = this.arr.map(row => {
// this === (outer this)
var mUPC = this.removeLeadingZero(row[0]);
// ...
});
Additionally, you could stop using this and new.

I have solved this issue and below is the answer in case anyone else runs into this:
this needs to be placed into a variable:
var _this = this;
and then you can call it within the object:
var mUPC = _this.removeLeadingZero(row[0])
Javascript scope strikes again!

Function composition in JavaScript

What's the benefit of function composition implementation in libs like underscore, lo-dash and others, similar to this one:
var compose = function() {
var funcs = arguments;
return function() {
var args = arguments;
for (var i = funcs.length; i --> 0;) {
args = [funcs[i].apply(this, args)];
}
return args[0];
}
};
var c = compose(trim, capitalize);
in comparison to this:
var c = function (x) { return capitalize(trim(x)); };
The latter is much more performant.

For one, it's easier to read. Performance is rarely more important than that. Also, you could make a dedicated arity 2 function with nearly the same performance.
The other benefit is the composition can be easily changed at runtime. You can create versions that trim before capitalization, capitalize before trimming, trim only, capitalize only, or neither, without having to explicitly specify every single combination in the code. This can greatly simplify your code sometimes. Runtime composition is one of those things you never knew you always wanted.
For example:
var c = function(x) {return x;} // identity
var onTrimClick = function() {c = compose(c, trim);}
var onCapitalizeClick = function() {c = compose(c, capitalize);}
var onSomethingElseClick = function() {c = compose(c, somethingElse);}
This lets you create a composed function c at runtime based on what the user clicks and in what order.

//A simple way to understand javascript function composition =>
function composition(...fun) {
return function (value) {
var functionList = fun.slice();
while (functionList.length > 0) {
value = functionList.pop()(value);
}
return value;
}
}
function mult2(value) {
return value * 2;
}
function mult3(value) {
return value * 3;
}
function mult5(value) {
return value * 5;
}
var composedFun = composition(mult2, mult3, mult5);
console.log(composedFun);
console.log(composedFun(1));
console.log(composedFun(2));

Are there any behavioural differences before and after this javascript refactoring?

I recently had to refactor a chunk of javascript that is using YUI.
So, originally it was something like this:
YAHOO.namespace('space.time');
YAHOO.space.time = (function() {
var b = document.getelementbyid("aifdsgyalierg");
function c(b) {
var a = new YAHOO.util.Anim(d, b); //just assume the parameters are correct here
a.method = YAHOO.util.Easing.easeOut;
a.animate();
};
return { c:c };
})();
For the sake of being able to inject dependencies, i refactored it to the below:
YAHOO.namespace('space.time');
YAHOO.namespace('space.timefn');
YAHOO.space.timefn = function(yuianim) {
var b = document.getelementbyid("aifdsgyalierg");
function c(d) {
var a = new yuianim(d, b); //just assume the parameters are correct here
a.method = YAHOO.util.Easing.easeOut;
a.animate();
};
return { c:c };
};
YAHOO.space.time = YAHOO.space.timefn(YAHOO.util.Anim);
So..
1) Ignoring any committed fallacies.. Will the behaviour of the two snippets differ?
2) What fallacies have i committed?

How to create a javascript library using a closure

I have written some javascript that I would to encapsulate in a closure so I can use it elsewhere. I would like do do this similar to the way jQuery has done it. I would like to be able to pass in an id to my closure and invoke some functions on it, while setting some options. Similar to this:
<script type="text/javascript">
_snr("#canvas").draw({
imageSrc : someImage.png
});
</script>
I have read a lot of different posts on how to use a closure to do this but am still struggling with the concept. Here is where I left off:
_snr = {};
(function (_snr) {
function merge(root){
for ( var i = 1; i < arguments.length; i++ )
for ( var key in arguments[i] )
root[key] = arguments[i][key];
return root;
}
_snr.draw = function (options) {
var defaults = {
canvasId : 'canvas',
imageSrc : 'images/someimage.png'
}
var options = merge(defaults, options)
return this.each(function() {
//More functions here
});
};
_snr.erase = function () {};
})(_snr);
When ever I try to call the draw function like the first code section above, I get the following error, '_snr is not a function'. Where am I going wrong here?
EDIT
Here is what I ended up doing:
function _snr(id) {
// About object is returned if there is no 'id' parameter
var about = {
Version: 0.2,
Author: "ferics2",
Created: "Summer 2011",
Updated: "3 September 2012"
};
if (id) {
if (window === this) {
return new _snr(id);
}
this.e = document.getElementById(id);
return this;
} else {
// No 'id' parameter was given, return the 'about' object
return about;
}
};
_snr.prototype = (function(){
var merge = function(root) {
for ( var i = 1; i < arguments.length; i++) {
for ( var key in arguments[i] ) {
root[key] = arguments[i][key];
}
}
return root;
};
return {
draw: function(options) {
var defaults = {
canvasId : 'canvas',
imageSrc : 'images/someimage.png'
};
options = merge(defaults, options);
return this;
},
erase: function() {
return this;
}
};
})();
I can now call:
<script type="text/javascript">
_snr("#canvas").draw({
imageSrc : someImage.png
});
</script>

Because you declared _snr as an object and not a function. Functions can have properties and methods, so there's various ways to achieve what you want, for example one of them would be say...
_snr = function(tag) {
this.tag = tag;
}
_snr.foo = function() {
//Code goes here
}
You can also pass the outer context into a closure to hide your variables from accidentally polluting the global namespace, so like...
(function(global) {
var _snr = function(tag) {
this.tag = tag;
}
_snr.foo = function() {
//Code goes here
}
//export the function to the window context:
global._snr = _snr;
})(window);
window._snr('#tag').foo('wat');
Happy coding.

Because your _snr is an object, not a function. You have to call it like this:
_snr.draw({
canvasId: '#canvas',
imageSrc: 'someImage.png'
});

When you do _snr('#canvas') that is a function call which is why you're getting that error. _snr is an object with some methods attached to it such as draw() and erase(). The reason jQuery is able to pass arguments into the $ is because they return the $ as a function object which is why we're able to pass it various selectors as arguments.

You are going wrong at the first line _snr = {}
It needs to be
_snr = function(){
selector = arguments[0]||false;
//snr init on dom object code
return _snrChild;
}
Im on a mobile phone but when im on a pc I will maybe fix the whole code c:

Here you have a snr object and that has erase and draw methods. What you intend to do is to write a _snr function which will get an id and return a wrapper object. That returned object should have erase and draw methods. so you can do
var returnedObject = _snr("my_id");
returnedObject.draw("image.png");