How to use JavaScript comparison operators and logical operators

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JavaScript data type

String, number, Boolean, array, object, Null, Undefined

JavaScript has dynamic types

JavaScript has dynamic types. This means that the same variable can be used as different types:

Var x / / x is undefinedvar x = 6; / / x is a number var x = "Bill"; / / x is a string

JavaScript string

A string is a variable that stores characters, such as "Bill Gates".

The string can be any text in quotation marks. You can use single or double quotation marks:

Var carname= "Bill Gates"; var carname= "Bill Gates"

You can use quotation marks in a string, as long as they do not match the quotation marks that surround the string:

Var answer= "Nice to meet you!"; var answer= "He is called" Bill ""; var answer= "He is called" Bill ""

JavaScript digit

JavaScript has only one numeric type. Numbers can be decimal or not:

Var x1 to 34. 00; / / write var x2 to 34 with decimal point; / / write without decimal point

Very large or very small numbers can be written by scientific (exponential) counting:

Var yearly 123e5; / / 12300000var zonal 123eMur5; / / 0.00123

JavaScript Boolean

Boolean (logical) can only have two values: true or false. Boolean is often used in conditional testing.

Var x=truevar y=false

JavaScript array

The following code creates an array named cars:

Var cars=new Array (); cars [0] = "Audi"; cars [1] = "BMW"; cars [2] = "Volvo"

Or (condensed array):

Var cars=new Array ("Audi", "BMW", "Volvo")

Or (literal array):

Var cars= ["Audi", "BMW", "Volvo"]

Example

Var i; var cars = new Array (); cars [0] = "Audi"; cars [1] = "BMW"; cars [2] = "Volvo"; for