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The name also shows up in the debugger and some stack traces, which can save you time when debugging.
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.
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.
Below we will introduce you to some aspects of the core language, and you'll also play with a few browser API features too.
Important: If you haven't been following along with the rest of our course, download this example code and use it as a starting point.
First, go to your test site and create a new folder named scripts. Then, within the new scripts folder you just created, create a new file called main.
Save it in your scripts folder. Next, in your index.
Now add the following code to the main. What happened? Your heading text has now been changed to "Hello world! You did this by first using a function called querySelector to grab a reference to your heading, and store it in a variable called myHeading.
This is very similar to what we did using CSS selectors.Infinite backtracking problem.
Mutation observer. JS Reference.
It includes code structure, syntax, variables, operators, data types, functions and so on Advanced Features: Using OOPs methodology, error handling, debugging and understanding the usage of complex functions is detailed in this section. JS has been used.