JavaScript tutorial: null type

Article Introduction: The main purpose of our null reference here is to say that if we define a variable that will be used to store the object in the future, then we'd better initialize the variable to null, so as long as it detects null value to see if the variable has already saved a reference to an object.

A null type is the second data type with only one value, its value is null, and the null value represents an empty object pointer, so it is an object to detect null using the TypeOf operator. Element

Font
Font-family
Font-size
Font-style
Font-variant
Font-weight
Letter-spacing
Line-height
Text-decoration
Text-align
Text-indent
Text-transform
White-space
Word-spacing
Color
Background
Bg-attachment
Bg-color
Bg-image
Bg-position
Bg-repeat
Box
Width
Height
Border-top
Border-right
Border-bottom
Border-left
Margin
Padding
Max-height
Min-height
Max-width
Min-width
Outline-color
Outline-style
Outline-width
Positioning
Position
Top
Bottom
Right
Left
Float
Display
Clear
Z-index
List
List-style-image
List-style-type
List-style-position
Table
Vertical-align
Border-collapse
Border-spacing
Caption-side
Empty-cells
Table-layout
Effects
Text-shadow
-webkit-box-shadow
Border-radius
Other
Overflow
Cursor
Visibility

The main purpose of our null reference here is to say, if we define a variable that will be used to store the object in the future, then we'd better initialize the variable to null, so that it's possible to know whether the variable has saved a reference to an object as long as it detects a null value. var car = null; if (car!= null) {}