Summary
formatMoney takes a value and returns that value formatted nicely as money, as a string.
The user can specify formatting settings like currency symbol, separator, etc.
They can do this via a long list of parameters, or by passing in an options object.
Because of this, the code is long, convoluted, and difficult to read.
It would be better to only allow the user to specify formatting by passing in a format object.
Read on for line-by-line notes.
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Summary
We can round numbers more consistently if we use scientific notation.
First we move the decimal with something like '1.005e2'
Then we round this exponential form with Math.round.
Finally, we move the decimal back to it's original position with 'e-2".
Read on for a detailed walkthrough.
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Summary
Javascript doesn't round the way we want in accounting software.
This is to do with some decimal numbers being not completely precise because computers have to think in terms of powers of 2.
AccountingJS creates its own toFixed method that essentially does this:
Multiply to get the number to only one decimal place
Use Math.round to round using more predictable behavior
Then divide the number back down to get it to the number of decimal places you wanted.
Read on to see the full walkthrough.
Summary:
checkCurrencyFormat takes an argument, format that can be a string, object, or function.
It returns a format object
So if the format parameter is a string, it changes it to an object and returns it.
If format is a valid object, it simply returns it back, untouched.
If format is an invalid object, it uses the default (lib.settings.currency.format) and changes it to an object if it isn't already.
Continue reading to see the full walkthrough.
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Summary
AccountingJS’s map() function checks to see if the native Array.prototype.map function is available.
If the native map is available, it uses it.
If not, it uses its own implementation.
Click on to see a detailed walkthrough.
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Summary
The defaults() function allows you to pass in two objects and apply the properties from the second object to the first one where those properties don't already exist on the first object.
It does this by enumerating through each property on the second object and checking to see if that property exists on the first object. If the property doesn't exist, it applies that property to the first object.
This is a way to only need to define "custom" properties when creating a new object, and then setting all the "standard" options to the defaults set in another "default" object.
Read on to see how this all works in detail.
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Repetition is the mother of skill. If you want to get good at something, you just have to practice. It's that simple, but consistency is key.
I've been using an app called Streaks to help me stay on top of my goal of doing 1 hour of Javascript every day.
The app is simple, you "check in" to an activity when you do it, and over time you can see how many days you hit and how many you missed. The idea is to get addicted to maintaining your streak. Having a visual representation of your consistent hard work is rewarding and reinforces good behavior.
Let's see how high I can get this streak!
Summary:
isArray
Tells you whether something is an array or not.
Uses the native isArray if browser supports ES5 or later.
Uses hand-rolled implementation if not.
.call()
a nice trick to borrow a method from one object and call it on another.
when you use .call(object) you set the this value to object for whatever is to the left of the dot.
AccountingJS uses Object.prototype.toString(obj) to show us the type of obj (and uses an equality check).
isObject
Uses same techniques as isArray, but instead checks to see if something is a plain object (not an array, string, number, etc.).
Click “Read more” to see the full explanation.
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Summary
The best way to get into a new code base is to understand the simple pieces, this will help you understand the more complex pieces.
AccountingJS has two main sections: Internal Helper Methods, and API Methods.
The Internal Helper Methods are a good place to start because there are some simple methods in there that are easy to understand and are used in the API methods.
The isString method uses !! to get the corresponding boolean value of what comes after it.
Boolean() is a cleaner alternative to !!
Strings can have methods because Javascript creates an object version of your string using the new String constructor method, so it can put methods on the prototype. When you call these methods, it uses the object version of your string, returns the value, then throws it all away behind the scenes.
Summary
We can use constructor functions to create new objects that have shared properties.
An object created by a constructor function has its prototype property set to an object automatically created by the constructor function. For example, Dog.prototype.
We can add functionality to Dog.prototype and all instances of dog will have that functionality.
Array.prototype.forEach() is an example of this.
Summary:
Prototypes allow us abstract commonalities between objects out into a prototype object so they can be "born" with certain data and abilities.
It allows us to avoid repetition.
Even the most basic object already has a default object prototype that gives it certain "innate" abilities like "hasOwnProperty", and other methods.
The main idea of today's exercise is that we looked at the noConflict implementation in Accounting JS, and wrote a new version that was simpler.
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Summary:
noConflict is a common technique to allow dual-use of the same variable name, useful with libraries.
Summary:
We can see the same if/else logic in Accounting JS that we used in with sandwichLibary.
The idea is that it dynamically detects if you are using a given system, and then runs implementation code specific to that system
If there is no system, the last resort is to simply attach the library to the Window object.
A year ago a read another book by Jason Fried, Rework, and it transformed my thinking about how approach my career and work. The year since reading that book has been the best year of my career by every important metric. So I decided to try another book of his called "Remote: Office Not Required".
Jason Fried is the founder of 37signals, creators of Basecamp, Ruby on Rails, and other great collaboration tools. His impact on the industry is undeniable.
In this book he lays out the argument for why Remote work is the future of work, and why businesses to fail to embrace it put themselves at a serious disadvantage.
Here are some snippets from the book that stuck with me:
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Summary
When building a library, we don’t know if the developer prefers to create a global variable on the window object for every library, or use librarySystem.
To solve this, we can create an if/else statement that checks to see if librarySystem exists.
If librarySystem exists, we call the librarySystem function.
If librarySystem doesn’t exist, we attach sandwichLibrary directly to the window object.
Summary
Attaching libraries to the window object is a good way of reducing the number of global variables (and potential naming conflicts).
But if you have 100 or 1,000+ libraries, you would still have a lot of global variables.
There is another approach that allows us to expose a single global variable, such as "librarySystem", which is a function that lets us grab libraries by name, and create new ones.
Specifically:
1. Create: librarySystem('libraryName', function() { /* return library */});
2. Use: librarySystem('libraryName'); ==> returns library object
Summary:
Functions can always remember the variables they could see at creation.
They can see variables defined inside the function.
They can see variables defined in enclosing functions.
"Get the fundamentals down and the level of everything you do will rise" - Michael Jordan
Today I'm starting something new on this blog. This year, one of my goals has been to master javascript fundamentals. I've created projects in the past using Javascript, Objective-C, Swift, and Ruby - but because my goal was always to build something, I never built a rock solid foundation of knowledge. I would google and hack my way to solutions, but my speed and enjoyment suffered by the fact that I hadn't mastered the fundamentals.
In design, I have such an intuitive understanding of the principles, best practices, and tools - that I'm able to move quickly and happily from problem to solution. I want this fluid sense of mastery in code as well.
What I'm doing about it: Since December 2017, I've set the goal of 1 hour of learning Javascript everyday with the goal of mastering the fundamentals. Sure, I've missed days along the way as work requirements demand extra time, etc. - but I've done my best to stick to this regimen and it's paying off.
How I'm learning: I do 1 hour of video lessons from Watch and Code every day. If you're interested in learning Javascript in a way that goes beyond basic tutorials and gives you a foundational, practical knowledge without relying on frameworks - I'd highly recommend it. I've learned a lot of skills on the internet, and this is without a doubt one of the best programs I've found.
As I move forward with documenting my progress on this blog, I'll be keeping my notes on the blog to force me to clarify my understanding (to the point of being able to explain it). If you're reading these posts, please keep in mind that these are just my notes, and I'm not an expert (yet!). If your goal is also to master the fundamentals of Javascript, please head over to Watch and Code and start your journey there!
Anyway, that's what's going on here now - so I'll just jump in to today's notes:
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Chapter 5: AccountingJS
Lesson 4: IIFEs and sharing data
We use IIFEs so we can hide variables from the rest of the program, so we can avoid potential conflicts
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