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Java Script Data Types

By Stephen Bucaro

Programs work with data. A data type specifies what kind of data, for example a number or a string of characters. The type of a piece of data is important because it determines what kind of data can be stored in it and what operations can be performed on it. For example, you can multiply the number 2 by the number 3 to get the result 6. But if you multiply the character "2" by the character "3", you get nonsense results.

Data types can be broken down into two categories, primitive and composite. Primitive data types, like the integer, are the simplest. Composite data types, like the object, are composed of several primitive data types.

Primitive Data Types

JavaScript supports several primitive data types.

• Integer
• Floating-point number
• String
• Boolean

Integers are whole numbers, either positive or negative. Integers are usually expressed in decimal (base 10) notation, for example 123, but they can also be expressed in hexadecimal or octal notation.

Hexidecimal (base 16) notation is commonly used when referring to data as it's stored in a computers memory. A hexadecimal data type is indicated by starting a number with 0x, for example 0x7aff.

Octal (base 8) notation was used when referring to data as its stored in a 4-bit memory cell and is now obsolete. An Octal data type is indicated by starting a number with 0, for example 0275.

Floating-point numbers are fractional numbers, either positive or negative. Floating-point numbers are usually expressed by including a decimal point, for example 123.45, but when expressing very large or very small numbers, they can be expressed in exponential notation. Numbers expressed in exponential notation include a decimal point along with the letter e, for example 1.234e8.

Strings are a row of one or more characters, for example a word or a paragraph. A string is expressed by enclosing it in quotes, for example "hello". The quotes can be either single or double, but the starting quote must match the ending quote. If you want to use a quote character within your string, enclose the string in the opposite kind of quote, for example 'I said "hello" to you'.

Booleans are logical values that can be expressed as either true or false. Booleans are commonly used when making tests or comparisons. For example, if logged-in equals true, then permit access, if logged-in equals false, block access. During computation true evaluates to 1 and false evaluates to 0.