Array.map Vs. forEach

This is one of the concepts where people get confused. Every one thinks that Array.map function and forEach for an Array is the same, but which is not. Lets try to differentiate:
1. forEach
forEach can be used with any array to iterate through each and every value. It's just like using a traditional 'for loop' that starts with 1 and goes through the end element.

 let array = [10,20,30,40,50];  
 array.forEach((number)=>{  
  console.log(number);  
 })

The above code will generate the following output.
10
20
30
40
50
2. Array.map
The map function creates a new Array with the result of calling the given function or expression on every elements of the Array.

 var result = array.map((number)=>{  
  return (number * 2);  
 });  
 console.log(result);

The output of the code is:
[ 20, 40, 60, 80, 100 ]
In the above example we are trying to iterate through every element of Array and multiply it by 2. The resultant applied on every element will be also an array.
Happy Coding! | dhandrohit@gmail.com

Comments

How to use QueryExtenderControl in ASP.NET with LINQ

Queryextender control is a control that helps in doing actions like filtration, searching, sorting etc. on the LINQ Data source with few steps. In fact we don’t have to write any code with this. Screenshot given below is just an example that can easily be achieved through this control. In the above screenshot, we can see that there is a GridView Control that has been binded to a LINQData Source Control. And we have a DropDownlistBox that is also binded to another LINQData Source Control and displaying only grouped jobs. The GridView display all the employees who are matching the Job Parameter. This is done through QueryExtender Control. Also we can search for any name in the employee name's through Query Extender control. The code in the HTML goes like: < form id ="form1" runat ="server"> < div > Select Job: < asp : DropDownList ID ="Job" runat ="server" DataSourceID ="LinqDataSource2...

Using GUID or UniqueIdentifiers in SQL Server

In order to differentiate between two rows, we normally use primary keys or identity values which may be same across two tables. In order to overcome this problem we can use a special type named "GUID" . Its a hexadecimal number (Base 16) and the advantage is that they are unique across all databases and tables. In SQL Server the same concept is implemented through UNIQUEIDENTIFIER data type. In order to generate a new value, we use the NEWID() function. For e.g. a. Creating a table that uses the UNIQUEIDENTIFIER datatype Create table Test ( Empno uniqueidentifier, Ename varchar(20) ) b. Inserting rows in the tables with the use of NEWID() function insert into Test values (newId(),'ABC') insert into Test values (newid(),'XYZ') insert into test values (newid(),'MNO') c. Selecting the rows from the table. Select * from test Empno ...

How to Delete Record through Knex.

This post is all about of deleting records through KNEX ORM in Nodejs. The following code shows how to achieve this: knex("depts").where("deptno","50").del() .then(function (count) { console.log(count); }) .finally(function () { knex.destroy(); }); The above code deletes a record from a table "Depts" where Deptno = 50. It has a "then" Promise attached that will show how many records were deleted with this command. Also "finally" is the method that will always execute and will close the KNEX connection. Happy Coding !!!

Rohit Dhand

Search This Blog