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This allows more optimizations to be done by the engine and results in more readable code.
There are two ways in which the name might be displayed: as "first last" or as "last, first". You end up with dozens of functions in your global namespace. What we really need is a way to attach a function to an object. Used inside a function, this refers to the current object. What that actually means is specified by the way in which you called that function. If you called it using dot notation or bracket notation on an object, that object becomes this.
If dot notation wasn't used for the call, this refers to the global object. Note that this is a frequent cause of mistakes. Since there are no global variables called first or last we get undefined for each one.
It creates a brand new empty object, and then calls the function specified, with this set to that new object. Notice though that the function specified with this does not return a value but merely modifies the this object. It's new that returns the this object to the calling site. Functions that are designed to be called by new are called constructor functions.
Common practice is to capitalize these functions as a reminder to call them with new. The improved function still has the same pitfall with calling fullName alone. Our person objects are getting better, but there are still some ugly edges to them. Every time we create a person object we are creating two brand new function objects within it — wouldn't it be better if this code was shared?
As a result, anything assigned to Person. This is an incredibly powerful tool. The root of that chain is Object.
We can revisit that now. The first argument to apply is the object that should be treated as 'this'.
For example, here's a trivial implementation of new: function trivialNew constructor, This is not something you use very often, but it's useful to know about. In this snippet, We've seen this once before, with an earlier makePerson function. If a called function relies on one or two other functions that are not useful to any other part of your code, you can nest those utility functions inside it.
This keeps the number of functions that are in the global scope down, which is always a good thing. This is also a great counter to the lure of global variables. When writing complex code it is often tempting to use global variables to share values between multiple functions — which leads to code that is hard to maintain.
Nested functions can share variables in their parent, so you can use that mechanism to couple functions together when it makes sense without polluting your global namespace — "local globals" if you like. This technique should be used with caution, but it's a useful ability to have.
Table of contents
There may be typos, please use the "Edit on Github" link in left sidebar in an article, at the bottom to propose fixes. Modifying the document. In July , the disparate parties on either side came together in Oslo. Tutorial map. Every time we create a person object we are creating two brand new function objects within it — wouldn't it be better if this code was shared?
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