Javascript Sets Cookies

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Cookies are both a delicious snack and a crucial part of modern sites.

Cookies allow you to store data about a user in the web browser. Cookies often store information such as authentication sessions so that the browser remembers that you are logged into a web page.

In this guide, we are going to talk about why cookies exist, such as what types of cookies are present and how to use JavaScript cookies. Let’s get started!

What are the cookies of your browser?

Cookies are text strings that store information about a user in the browser. The idea was started by Netscape, which developed one of the most popular browsers in the world in the 1990s. Netscape developed cookies to track whether a user has visited their site before. If they did, it probably meant that the user knew something about Netscape.

Cookies must contain at least one name and one value field. The name field is used to identify the contents of the value field. A cookie can store additional attributes, such as a file path and when it expires, depending on how cookies are used in applications

Here is an example of a cookie.

cookies are stored in the key: pairs of values. When you view this cookie, you will see the following:

This cookie is used to store the AUTHENTICATION_KEY value in your browser. Each time you access the python.engineering domain, this cookie is made available on the site.

There is no limit to how many cookies you can set for a site, but what you will find is that most apps only need to save a bit, if necessary. Often cookies are used to track a user session

Retrieve browser cookies

JavaScript has an object called document.cookie which stores information about all the cookies available on a site. To set, update and delete cookies , we need to manipulate this object. To retrieve the cookies, we can simply call this object:

This code returns a list of all cookies in the browser. It is not possible to retrieve a cookie from this list without writing a custom function to do so.

How to configure a browser cookies

How can I configure a browser cookie? Well, there is one thing you should know up front: it’s probably easier than baking your own cookies

Let’s say you want to store it in an email cookie of a user ... We could make u sing this JavaScript code:

This code creates a cookie with the name "email" and the value " [email protected] ". Our console.log () statement returns the following:

You can also specify a path where a cookie is available:

This code would be" email " cookies available on all paths starting with" / dashboard ". By default, cookies are deleted

cookie expiration dates

when the browser is closed. When setting a cookie, you can optionally add an expiration date that replaces this parameter:

This will create a cookie that expires on June 24, 2020, at the start of the day. The expiration date must be specified in UTC time.

A common approach to setting an expiration date is to use the JavaScript Date object, which returns a UTC timestamp. A cookie set expires on June 30, 2020 would use this code:

The document.cookie object supports setting a maximum age for a cookie, or Max -age, which indicates how long a cookie must be available before expiring. Although not supported by all browsers, it simplifies the creation of cookies which expire based on when the user initiated the creation of the cookie:

This will create a cookie which expires after two days.

Updating and deleting cookies

There are no functions used to update or delete cookies, but a change is made to the "document.cookie" object .

you can update a cookie the same way you created it:

This changes the value of "e - mail" to " [email protected] " to "[email protected]".

deleting a cookie uses a similar approach. All you need to do is use the same syntax used to create or update a cookie, but remove the value assigned to the cookie:

You must specify a path to make sure you delete the correct cookie

Types of cookies

raspberry. Chocolate Chip. To swindle. No, not these types of cookies! There are three main types of cookies in the browser: Session, third and persistent

cookies session are cookies that exist until the browser is closed .. These are the cookies without date expiration, like the one in our first example. It should be noted that some developers use the term "session cookie" to refer to any cookie that authenticates a user, but session cookies are not the only cookies you can use for authentication.

Persistent cookies are cookies that exist even after closing the browser. These are cookies with a set of expiration date.

Third party cookies are cookies set by other sites. An example of this are Google Analytics cookies . If you install Google Analytics on your site, the extension will be able to set cookies to track users.

Conclusion

Cookies are a convenient way to store information about the user. User the browser. They are often used to monitor whether a user has visited a site before and to store authentication cookies

There are three main types of cookies: session, persistent and third party. For your applications, you will mainly focus on the use of session and persistent cookies.

Javascript Sets Cookies __del__: Questions

__del__

How can I make a time delay in Python?

5 answers

I would like to know how to put a time delay in a Python script.

2973

Answer #1

import time
time.sleep(5)   # Delays for 5 seconds. You can also use a float value.

Here is another example where something is run approximately once a minute:

import time
while True:
    print("This prints once a minute.")
    time.sleep(60) # Delay for 1 minute (60 seconds).

2973

Answer #2

You can use the sleep() function in the time module. It can take a float argument for sub-second resolution.

from time import sleep
sleep(0.1) # Time in seconds

__del__

How to delete a file or folder in Python?

5 answers

How do I delete a file or folder in Python?

2639

Answer #1


Path objects from the Python 3.4+ pathlib module also expose these instance methods:

Javascript Sets Cookies __delete__: Questions

2639

Answer #2


Path objects from the Python 3.4+ pathlib module also expose these instance methods:

2639

Answer #3

Python syntax to delete a file

import os
os.remove("/tmp/<file_name>.txt")

Or

import os
os.unlink("/tmp/<file_name>.txt")

Or

pathlib Library for Python version >= 3.4

file_to_rem = pathlib.Path("/tmp/<file_name>.txt")
file_to_rem.unlink()

Path.unlink(missing_ok=False)

Unlink method used to remove the file or the symbolik link.

If missing_ok is false (the default), FileNotFoundError is raised if the path does not exist.
If missing_ok is true, FileNotFoundError exceptions will be ignored (same behavior as the POSIX rm -f command).
Changed in version 3.8: The missing_ok parameter was added.

Best practice

  1. First, check whether the file or folder exists or not then only delete that file. This can be achieved in two ways :
    a. os.path.isfile("/path/to/file")
    b. Use exception handling.

EXAMPLE for os.path.isfile

#!/usr/bin/python
import os
myfile="/tmp/foo.txt"

## If file exists, delete it ##
if os.path.isfile(myfile):
    os.remove(myfile)
else:    ## Show an error ##
    print("Error: %s file not found" % myfile)

Exception Handling

#!/usr/bin/python
import os

## Get input ##
myfile= raw_input("Enter file name to delete: ")

## Try to delete the file ##
try:
    os.remove(myfile)
except OSError as e:  ## if failed, report it back to the user ##
    print ("Error: %s - %s." % (e.filename, e.strerror))

RESPECTIVE OUTPUT

Enter file name to delete : demo.txt
Error: demo.txt - No such file or directory.

Enter file name to delete : rrr.txt
Error: rrr.txt - Operation not permitted.

Enter file name to delete : foo.txt

Python syntax to delete a folder

shutil.rmtree()

Example for shutil.rmtree()

#!/usr/bin/python
import os
import sys
import shutil

# Get directory name
mydir= raw_input("Enter directory name: ")

## Try to remove tree; if failed show an error using try...except on screen
try:
    shutil.rmtree(mydir)
except OSError as e:
    print ("Error: %s - %s." % (e.filename, e.strerror))

__delete__

Is there a simple way to delete a list element by value?

5 answers

I want to remove a value from a list if it exists in the list (which it may not).

a = [1, 2, 3, 4]
b = a.index(6)

del a[b]
print(a)

The above case (in which it does not exist) shows the following error:

Traceback (most recent call last):
  File "D:zjm_codea.py", line 6, in <module>
    b = a.index(6)
ValueError: list.index(x): x not in list

So I have to do this:

a = [1, 2, 3, 4]

try:
    b = a.index(6)
    del a[b]
except:
    pass

print(a)

But is there not a simpler way to do this?

1055

Answer #1

To remove an element"s first occurrence in a list, simply use list.remove:

>>> a = ["a", "b", "c", "d"]
>>> a.remove("b")
>>> print(a)
["a", "c", "d"]

Mind that it does not remove all occurrences of your element. Use a list comprehension for that.

>>> a = [10, 20, 30, 40, 20, 30, 40, 20, 70, 20]
>>> a = [x for x in a if x != 20]
>>> print(a)
[10, 30, 40, 30, 40, 70]

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