Awesome Explanation…. Must Read!
undefined vs null in javascript
Null and undefined are the most confusing datatypes of JavaScript. It might be in the history of confusing topics 🙂
In simple words:
undefined : undefined variable or property
null : property does exist, but holds no value
Let’s see some example for better understanding
Step 1:
console.log(x); // Uncaught ReferenceError: x is not defined
Step 2:
var x;
console.log(x); // undefined
alert(typeof x); // undefined
In Step 2, if you see x is defined but still it says its ‘undefined’ when we print it. Because, its defined but it do not have any value in it.
Step 3:
var y = null;
console.log(y); // null
alert(typeof y); // object
null is a type of default value for a variable independent of type of variable.
From the preceding examples, it is clear that undefined and null are two distinct types: undefined is a type itself (undefined) while null is an object.
Conclusion
null is an empty value
undefined is a missing value
null is a special keyword, not an identifier, and thus you cannot treat it as a variable to assign to. But, undefined is an identifier. In both non-strict mode and strict mode, however, you can create a local variable of the name undefined (not recommended).
Enjoy Coding!
How to manage file having similar name in S3 bucket?
Default S3 bucket settings do not allow multiple files with same name. When you try to upload file with name which is already present in your S3 bucket, it will overwrite the file without any warning. To avoid overwriting with same name in S3 bucket, can be achieved by Versioning enabled S3 Bucket.
What a Version enabled S3 Bucket benefits?
– Allows you to maintain various files with same name. Here, S3 auto manages to respond to file by selecting the latest version among various files present in S3.
– Can preserve, retrieve, and restore every version of overwritten and deleted objects in your Bucket.
– Can list the version(s) of any particular Amazon S3 Object or you can list all of the versions of all of the objects, which have been overwritten or deleted from an Amazon S3 bucket.
– Can manage destroying of the version files based on custom rules i.e. Life Cycle Management.
How to enable versioning in S3?
1. Choose the S3 bucket you want to enable for versioning.
2. Go to Properties of the bucket
3. Now, Select Versioning tab and Enable Versioning
4. Versioning you enabled, but to keep our bucket clean time to time. Need to set Life Cycle of the Versioning. Go to LifeCycle tab, where you can rule.
5. Can specify you want to add this life cycle to complete bucket or any specific folder of that bucket.
6. Set rule for the current version and the previous version of files in bucket i.e how long they will be active or will be deleted.
7. Review your rule and name to your rule, then Activate your rule.
Example:Â
Upload a file in your bucket and then upload same/another file with same name in the bucket. Then you will see versions of the file.
Its Done! Enjoy Coding. 🙂
Create docs for Rest API in just few clicks!!!
As APIs are getting more popular day by day either consuming any service in your application or provide any service to others. API documentation become a crucial part of making your API easy to understand and use.
I think documentation is like a recipe through which a person knows “what a person is trying and how to achieve”. Just as chefs rely on well-written recipes to create wonderful dishes, you need to create API documentation that is informative, succinct, and easy to read so other developers can cook up something wonderful using your APIs. 🙂
Remember while creating API Document:
– Should be from user’s perspective
– Be consistent (help yourself too while code)
– Should be in designed manner (not as plain text)
– URIs should be more clear as they are the most obvious thing in your documentation requires users to figure out mapping between your logic and the HTTP client.
– Give some example of usage and combine them with your explanation.
There are various tools/ways to create docs for your existing or new API, below I am going to show you how you can create your own interactive API documentation for your New or existing API using Postman REST Client+Swagger+Api transformer.
Here, are the steps:
References:
Enjoy Coding! 🙂
Using multiple Ternary Operator
Tip for using ternary operator
I faced some non-obvious behavior of Ternary Operator while working, actually I was using more than one ternary operator within single statement something like.
<?php
echo ( 1 == 1 ) ? ‘pass’ : ( 1 == 2 ) ? ‘fail’ : ‘other’;Â
// Expected output is ‘pass’ but it will give ‘fail’
?>
This behavior is because ternary expressions are evaluated from left to right. So, lets again look to above example.
To write in more advanced way the above code to get expected output. You need some parentheses around the right hand operand:
<?php
echo (1 == 1) ? ‘pass’ : ((2 == 2) Â ? ‘fail’ : ‘other’);
 // Will give output as ‘pass’
?>
I hope this will help.
Enjoy Coding! 🙂
Remove Virtual Host from Ubuntu!
It’s quite easy.
We create virtual host in path /etc/apache2/sites-available
To remove virtual host, just need to run this command in terminal.
sudo a2dissite sitename
After, running this command.
Restart apache server.
sudo service apache2 restart
And, its done!
Enjoy Coding! 🙂
MyISAM vs InnoDB….??
Storage Engines are the programs that are integrated with a MYSQL database management to manage the data tables. MYSQL supports different storage engines that handles different tables.
Selection of Storage Engine:
Selection of storage engine, depends on users table type and its purpose. Each has their own advantages and disadvantages. Also, possible to select engine at the time of creating tables.
While selecting storage engine, the factors that can affect your selection are:
- Transaction and concurrency
- Backups
- Special features
You should use INNODB for your tables unless you have a compelling need to use a different engine!! (To get High Performance)
By- Peter Zaitsev
Some of important Storage Engines are :
MyISAM, INOODB, MERGE, MEMORY, etc.
The major thing that one should know what are the difference between InnoDB and MyISAM???
MyISAM
(+)
- Designed with a thinking that database are frequently read not updated.
- Simple to understand and implement.
- Has…
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Grocery CRUD : CodeIgniter
Grocery Crud is a CodeIgniter CRUD. It is fully tested in codeigniter 2.0 and in 1.7.x. You don’t need so much line of codes, models , views, libraries to make a CRUD works. Just few lines need to write and a stable CRUD is ready.
Grocery CRUD is a codeigniter CRUD library that makes a php developer’s life easier.
Simple and many Features!
Even for complex CRUDs you can use it by adding callbacks. You can choose the CRUD template that you want to use by changing only the theme. You are able to build the grid and the forms easily and automatically by using the power of jquery.
The different themes currently available  are: 
- Datatables
- FlexGrid
- Twitter-Bootstrap
The good part is that you don’t even have to change the CSS to make it more user friendly. Grocery CRUD is ready for the production mode with all the required security and views.
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Something TECHIE 