Differential writing, weak variable type, tail score number may be optional, annotated as dual -inclined lines, parentheses indicate code blocks
2.2 variable
Variables are declared in VAR. The naming rules of variables: The first character must be a letter, an lower line or a US dollar symbol; the remaining characters can be the lower line, the US dollar symbol or any letter or digital character.
variable naming specifications:
Camel mark: The first letter is lowercase, and the next word starts with a capital letter. For example: Var mytestvalue = 0, mySecondTVALUE = “Hi”;
PASCAL mark: The first letters are capitalized, and the next word starts with uppercase letters. For example: Var mytestvalue = 0, mySecondTVALUE = “Hi”;
Hungary Type Method: Add a lowercase letter (or lowercase letter sequence) in front of the variable named after the Pascal mark, indicating the type of the variable. For example, I represent an integer, s represents the string, as shown below:
var iMyTestValue=0,sMySecondTestValue=”hi”;
The prefix used by the Hungarian type marking method defines the ECMAScript variables as follows:
Type: Array prefix: A Example: Avalues
Type: Boolean prefix: example B: BFOUND
Type: Floating -point prefix: F Example: Fvalue
Type: Function prefix: Fn Example: FnMethod
Type: Surgery prefix: I Example: IVALUE
type: Object prefix: O Example: OTYPE
type: regular prefix: Repatten
Type: String prefix: s example: SVALUE
Type: Variable Prefix: V Example: VVALUE
2.3 Keywords
The keywords defined by
ECMA-262 are::
break case catch continue default delete do else finally for function if in instanceof new return switch this throw try typeof var void while with
2.4 Reserved Word
ECMA-262 In the 3rd edition, the reserved words are::
abstract boolean byte char class const debugger double enum export extends final float goto implements import int interface long native package private protected public short static super synchronized throws transient volatile
2.5 Original value and reference value
Primitive value is a simple data segment stored in stacks, that is, their values are directly stored in the position of variable access.
Reference value is an object stored in the heap, that is, the value stored at the variable is a pointer, pointing to the memory of the storage object.
Author: Tian Xingjian, self -improvement