We hold data in variables. Variable is used as a container for our data. Think about holding a name.

Code:

var name="Poftut";
console.log(name);

• var is shortcut for variable. It is not a must but makes code readble. We can ommit the var while writing code
• name  is the name of the variable when we need to access the data we will use name
• = assigns “Poftut” to the name variable

Output:

Poftut

Types

As developing applications there will be a lot of different data to work. From numbers to logic true,false. We need to use some types to define our data.

Say we develop a calculator. We want to add numbers we can write a code like below.

num1=12;
num2=4;
console.log(num1+num2);

Number is a type for javascript and differently interpreted by Javascript engine. Javascript engine is the interpreter that exists in the browser to run Javascrip code.

Or expressing logic values like True, False is different from text values.

We will look details of this types next chapters.

Scope

Scope means a variable use able area. For example we can not use variables declared other than current file or we can not access a varibale defined outside of function

• Local Variable is only accessable from its scope
• Global Variable is access able from anywhere

Code:

myVar="Global";
function test(){myVar="Local";}
console.log(myVar);

Output:

Global

As we see a function creates its own scope and variables created in this local scope can not be accessed from global scope

Variable Names

Variable names can use different characters but there is some limitations.

• We can not use break as variable name because it is a keyword for Javascript and used by Javascript. It will create confussion and error to use break. Here is Javascript keywords.

abstract boolean break byte case catch char class const continue debugger default delete do double

else enum export extends false final finally float for function goto if implements import in

instanceof int interface long native new null package private protected public return short static super

switch synchronized this throw throws transient true try typeof var void volatile while with

• Variable names can not start with numbers. Which means
  • 12name is not valid variable name
  • name12  is valid variable name
• Javascript is case-sensitive language which is true for variable names. Myvar is different from MYVAR