Variables

JavaScript variables are containers used to store data values. The most common thing to use when writing JavaScript is “variables”. It is very simple to use. Let’s give it a small example.

        var x = 20;
        var y = "javascipt"

It is necessary to give the appropriate name when giving the names to the variables. This allows us not to be forced if we make changes to the code.

For example, a code like this is not wrong. But it leads to trouble in large projects:

        var number = "javascirpt";
        var text = [1,2,3]

For example, a code would be very accurate:

        var leonidas = "this is javascript"

Variable Analysis

        var web = "truecodes.org"

Let’s analyze this place.

• We have created a variable with “var” (variable).
• We named this variable as “web”.
• We matched this “web” variable to “truecodes.org”.
• If we use the name “web” in written codes then “truecodes.org” will return.

        document.write(web);
        //or
        console.log(web)

output:

truecodes.org

wrong use:

        x = 20;
        y = 10;
        document.write(x+y)

“var” can not be written without the variable.

JavaScript Variables Examples

Example 1

        var x = 20;
        var y = 10;
        document.write(x+y)

output:

30

Example 2

        var name = "true";
        var surname = "codes";
        document.write(
            "name    : " + name + "<br>" + 
            "surname : " + surname
            )

output:

name : true
surname : codes

Example 3

        var car = {
            name: "audi",
            date: 2019,
            model: "X",
        }

        document.write(
            "car name: " + car.name + "<br>"+
            "model   : " + car.model + "<br>" +
            "date    : " + car.date 
            )

output:

car name: audi
model : X
date : 2019

Points to Remember :

• Variable stores a single data value that can be changed later.
• Variables can be defined using var keyword. Variables defined without var keyword become global variables.
• Variables must be initialized before using.
• Multiple variables can be defined in a single line. e.g. var one = 1, two = 2, three = “three”;
• Variables in JavaScript are loosely-typed variables. It can store value of any data type through out it’s life time.

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