Variables are named container that holds some value.
In the following example we have created a variable name.
Variable name must not start with a digit and must not use reserved keywords.
Following are some of the valid variable names.
Following are invalid variable names.
var 1address; //invalid starts with digit
var student-name; //invalid using the - symbol
Variable names are case sensitive so, name and Name are considered as two separate variables.
We can use Camel Case to name variables. Its a typographic convention in which each word starts with a capital letter with no punctuations or space.
Following are some of the valid variable names using camel case.
We can also start the variable name using lower case letter for the first word and then upper case for the following words.
In order to declare multiple variables we can separate the variables using comma.
In the following example we have created 3 variables.
var studentName, studentID, studentAge;
We use the assignment operator = to assign value to a variable.
In the following example we have assigned the value 10 to the variable score.
var score = 10;
If a value is not assigned to a variable then it gets the undefined value.
Following code will print undefined in the browser console.
When a variable is re-declared then it retains its previous value.
In the following example we have declared a variable name and set it to "Yusuf Shakeel" and then re-declared it.
var name = "Yusuf Shakeel";
console.log(name); //this will print "Yusuf Shakeel"
console.log(name); //this will also print "Yusuf Shakeel"
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