JavaScript Data types

Each of the values of JavaScript is a data type of some kind.

In the ES5???, data type is divided into six kinds: five kinds of raw data types, the type of data types.

In the original data type?, divided into five categories:

Number (numeric) type: contains integers and floating-point numbers (that is, number);

Boolean (Boolean) type: Only true and false two values;

String (String) type: The string value must be enclosed in quotation marks, which can be single or double quotation marks;

Null type:? to indicate that a variable value is empty;

Undefined type:? To determine a variable that has been created but has no initial value.

The numeric type of JavaScript contains all the integer types and all floating-point types.

But don't distinguish between integers and floating-point numbers. Number indicates. Floating-point type floating-point type, that is, the value contains the integer part, the number of points and the part.

var num1 = 0.1; var num2 =. 1; //

Valid, but Nan Nan is not recommended as a special value for JavaScript, which means "? Number" (Not a numbers).

NaN is not a number, but its data type is type #.

Feature: Any operation that involves Nan will return Nan nan and not equal to any value, including Nan itself

Note: For these features, JavaScript provides the IsNaN () function.

This function is used to determine whether the calculated result is a numerical value.

If it is a number, returns False if it is not a number, which returns TRUE.

JavaScript data type raw data type (primitive type) number (numeric) type

Console.log (IsNaN (10)); False

Console.log (IsNaN ("Hello"));//True

JavaScript Data types