Monday, October 2, 2017
An Introduction to JSX
When React was first introduced, one of the features that caught most people's attention (and drew the most criticism) was JSX. If you're learning React, or have ever seen any code examples, you probably did a double-take at the syntax. What is this strange amalgamation of HTML and JavaScript? Is this even real code?
Let's take a look at what JSX actually is, how it works, and why the heck we'd want to be mixing HTML and JS in the first place!
What is JSX?
Defined by the React Docs as an "extension to JavaScript" or “syntax sugar for calling React.createElement(component, props, ...children))”, JSX is what makes writing your React Components easy.
JSX is considered a domain-specific language (DSL), which can look very similar to a template language, such as Mustache, Thymeleaf, Razor, Twig, or others.
It doesn't render out to HTML directly, but instead renders to React Classes that are consumed by the Virtual DOM. Eventually, through the mysterious magic of the Virtual DOM, it will make its way to the page and be rendered out to HTML.
How Does it Work?
JSX is basically still just JavaScript with some extra functionality. With JSX, you can write code that looks very similar to HTML or XML, but you have the power of seamlessly mixing JavaScript methods and variables into your code. JSX is interpreted by a transpiler, such as Babel, and rendered to JavaScript code that the UI Framework (React, in this case) can understand.
Don't like JSX? That's cool. It's technically not required, and the React Docs actually include a section on using “React Without JSX”. Let me warn you right now, though, it's not pretty. Don't believe me? Take a look.
JSX:
class SitePoint extends Component {
render() {
return (
<div>My name is <span>{this.props.myName}</span></div>
)
}
}
React Sans JSX:
class SitePoint extends Component {
render() {
return React.createElement(
"div",
null,
"My name is",
React.createElement(
"span",
null,
this.props.myName
)
)
}
}
Sure, looking at those small example pieces of code on that page you might be thinking, "Oh, that's not so bad, I could do that." But could you imagine writing an entire application like that?
The example is just two simple nested HTML elements, nothing fancy. Basically, just a nested Hello World. Trying to write your React application without JSX would be extremely time consuming and, if you're like most of us other developers out here working as characters in DevLand™, it will very likely quickly turn into a convoluted spaghetti code mess. Yuck!
Using frameworks and libraries and things like that are meant to make our lives easier, not harder. I'm sure we've all seen the overuse and abuse of libraries or frameworks in our careers, but using JSX with your React is definitely not one of those cases.
Continue reading %An Introduction to JSX%
by Matt Burnett via SitePoint
Pixelius
One Page portfolio for Spanish designer Emilio GarcĂa featuring a "pixelated" theme. Neat touch with the progress bar (in the fixed header) as you scroll.
by Rob Hope @robhope via One Page Love
How to Make Your Browsing Data More Private than a Thousand Incognito Windows [video]
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Understanding Args and Kwargs in Python
In this tutorial, I will be focusing on arguments (*args) and keyword arguments (*kwargs) in Python.
I will teach you what args and kwargs are and, most importantly, how to use them—that is how to take in an unlimited number of arguments and keyword arguments in functions.
What Are Args?
*args are used to pass non-keyword arguments. Examples of non-keyword arguments are fun(3,4), fun("foo","bar").
*args are usually used as a measure to prevent the program from crashing if we don’t know how many arguments will be passed to the function. This is used in C++ as well as other programming languages.
What Are Kwargs?
**kwargs is a dictionary of keyword arguments. The ** allows us to pass any number of keyword arguments. A keyword argument is basically a dictionary.
An example of a keyword argument is fun(foo=2,bar=7).
**kwargs are just like *args except you declare the variables and the amount within the function arguments.
Where to Use Args and Kwargs
Args and kwargs are useful when you want to:
- Reduce code rewriting.
- Make your code readable.
- Reuse your code
Using Args and Kwargs in Functions
Let's look at how kwargs and args are used in functions.
Args
The function below takes in three arguments. The three arguments have been explicitly defined, so any more or less will cause an error in the program.
def add(a, b,c):
print(a+b+c)
print add(2,3,4)
Let's run the function. The function will add the three numbers, giving the following output:
Output 9
What if we were to pass four arguments in the function instead of the required three? We will receive an error as shown below.
This is because only three parameters were defined in the function, but we have passed four positional arguments when calling the function.
def add(a, b,c):
print(a+b+c)
print add(2,3,4,5)
Output TypeError: add() takes 3 positional arguments but 4 were given
In the second example below, the * is for non-keyword arguments and gets passed into the function. Instead of having defined arguments, we replace a, b and c with a single parameter (*args).
Notice how the use of *args makes it easy to use any number of arguments without having to change your code. *args provide more flexibility to your code since you can have as many arguments as you wish in the future.
def add(*args):
total = 0
for arg in args:
total+=arg
print total
Scenario 1 print add(1,2,5) Output 8
Scenario 2 print add(1,2,5,6) output 14
Scenario 3 print add(1,2,5,8) Output 16
More Examples
Create a simple function as shown:
def func(*args):
# *args means for however many arguments you take in, it will catch them all
for arg in args:
print arg
Test the function using a combination of integers and strings:
def func(*args):
# *args means for however many arguments you take in, it will catch them all
for arg in args:
print arg
print func(11,3,4,5,"tuts")
Output 11 3 4 5 tuts
What if we were to pass a list as an argument? Test the function with a list by replacing the previous arguments with a list, l = [11,3,4,5,"tuts].
def func(*args):
# *args means for however many arguments you take in, it will catch them all
for arg in args:
print arg
l = [11,3,4,5,"tuts"]
print func(l)
This prints the list as a whole, This is because its interpreting the list as one item. Output [11,3,4,5,"tuts]
From the above example, you can also use *args to unpack arguments that are already in a list or a tuple so that all elements in the list are passed as different parameters.
Using the same function:
def func(*args):
# *args means for however many arguments you take in, it will catch them all
for arg in args:
print(arg)
l = [11,3,4,5,"tuts"]
print(func(*l))
The * will unpack the list and output each individual list item. Output 11 3 4 5 tuts
Kwargs
Kwargs allow you to pass keyword arguments to a function. They are used when you are not sure of the number of keyword arguments that will be passed in the function.
Write a function my_func and pass in (x= 10, y =20) as keyword arguments as shown below:
def my_func(x=10,y=20):
print x,y
This prints out the values of x and y Output 10,20
Kwargs can be used for unpacking dictionary key, value pairs. This is done using the double asterisk notation (**). It's important to note that each key must be matched with a value.
Here's a typical example of how it's done. The function below takes countries as keys and their capital cities as the values. It then prints out a statement which iterates over the kwargs and maps each keyword to the value assigned to it.
def capital_cities(**kwargs):
# initialize an empty list to store the result
result = []
for key, value in kwargs.items():
result.append("The capital city of {} is {} .format (key,value)
return result
You can call the function with any arguments you want.
def capital_cities(**kwargs):
# initialize an empty list to store the result
result = []
for key, value in kwargs.items():
result.append("The capital city of {} is {} .format (key,value)
return result
print capital_city(China = "Beijing",Cairo = "Egypt",Rome = "Italy"))
output ['The capital city of China is Beijing', 'The capital city of Cairo is Egypt','The capital city of Rome is Italy']
For a more complex example, suppose we have a model for a customer that looks something like this:
class Customer( models.Model ):
first_name = models.CharField(max_length = 100, null = True)
last_name = models.CharField(max_length = 100)
username =models.Charfield(max_length =100)
email = models.EmailField(max_length = 100)
password = models.CharField(max_length =100)
You can use kwargs to do both data inputs and data queries from model objects. Let's write a function view in order to create a new customer.
kwargs = {"first_name":"John","last_name":"Doe",
"username': "johndoe","email"johndoe@gmail.com",
"password":"1234"}
new_user = User(**kwargs)
new_user.save()
Here is how to perform a query of the customer we just created using kwargs.
filter_customer = {
'email':johndoe@gmail.com,
'username': johndoe,
}
Customer.objects.filter(**filter_customer)
Using Both Args and Kwargs in a Function
When using both args and kwargs in the same function definition, *args must occur before **kwargs.
class MyFunction(Foo):
def __init__(self, *args, **kwargs):
print 'my function'
super(MyFunction, self).__init__(*args, **kwargs)
Example:
def Func(*args,**kwargs):
for arg in args:
print arg
for item in kwargs.items():
print item
Remember args should come before kwargs.
def Func(*args,**kwargs):
for arg in args:
print arg
for item in kwargs.items():
print item
print Func(1,x=7,u=8)
Output
1
('x', 7)
('u', 8)
Conclusion
I hope this tutorial has helped you understand args and kwargs.
Below are some pointers to remember when using args and kwargs:
*argsand**kwargsare special syntax that are used in functions to pass a variable number of arguments to a function.*argsoccur before**kwargsin a function definition.*argsand**kwargsare best used in situations where the number of inputs will remain relatively small.- You can use any name you want;
argsandkwargsare only by convention and not a requirement. For example, you can use*fooinstead of*argsor**fooinstead of**kwargs.
The official Python documentation offers a lot of information for further study. Additionally, don’t hesitate to see what we have available for sale and for study in the marketplace, and don't hesitate to ask any questions and provide your valuable feedback using the feed below.
by Esther Vaati via Envato Tuts+ Code
Gin Lane
Beautiful, spacious One Page portfolio for NY-based digital agency, Gin Lane. The super long-scrolling Single Page site feature clean typography, lovely (enhanced) project imagery and a background color gradient that changes as you scroll. Final shout out to the responsive design, especially how well it fills a large screen 
by Rob Hope @robhope via One Page Love
How to Use Facebook Ads to Grow and Monetize Your Email List
Do you want more leads and sales from Facebook? Interested in remarketing to your email subscribers? In this article, you’ll discover how to use Facebook ads to build your email list, and then remarket to subscribers to increase your sales. #1: Create a Lead Magnet That Will Appeal to Your Target Audience You have to [...]
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- Your Guide to the Social Media Jungle
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