JavaScript Learning Notes

1. JavaScript is case-sensitive,

Single-line Comment

/**/Multi-line comments

2. Variables:

var quantity; declaring variables

Quantity = 3; variable assignment

Variable names begin with a letter, dollar sign, underscore, and cannot begin with a number. And you cannot use keywords and reserved words as variable names, usually using the hump naming method, such as Firstnameword,

3. Data type:

Number, string, undefined, Boolean, null, Oblect,array, Date,math, RegEx string expression: "" ' double quote, single quote,

4, array:

var color = [' white ', ' black ', ' Yellow ']; This method of creation is called an array literal;varnew Array (' White ', ' Pink ' ); This is an array constructor;varnew  Array (); Array.push ()   ; Inserting data Array.item (0); Get array data;
ARRAY[0]; Gets the array data; The index value of the array starts from 0 to the array length -1

5, Operator:

NaN (not a number)

Assigned value =

Arithmetic operator: +-*/% + +--

String operator: +

Comparison operators: > < >= <=! = = = = = = =!==

6, Function:

//basic structure of a functionfunctionChange () {return' Hellowolrd ';}//function CallChange ();//functions with ParametersfunctionChange (width,height) {returnwidth*height;}//function calls with parametersChange (20,30);

Functions that return multiple values

function GetSize (width,height,dept) {
var size = Width*height;
var clome = width*height*dept;
var sizes = [size, clome];
return sizes;
}

GetSize (100,20,30) [0]; Gets the return value of one

anonymous functions

var change = function () {
Return ' helloworld! ‘;
}

var value = Change (); Call

Call function expression immediately
var area = (function () {
var width = 3;
var height = 4;
return width*height;
}());

7, Object

//object creation: The literal methodvarText ={name:' Zhangsan ', Age:15, Sex:true, GetName:function(){return  This. Name;};//Accessing ObjectsvarName =Text.name;varName =text.getname ();varname = text[' name '];//Create object: constructor Syntaxvarhotel =NewObject (); Hotel.name= ' quart '; hotel.address= ' Beijing '; Hotel.getroom=function(){return(a) ;//Modifying Objectshotel[' name '] = ' HaHa ';//Delete ObjectDeletehotel[' name '] Use keyword delete;//constructor SyntaxfunctionHotel (name,age) { This. Name =name; This. Age =Age ; This. Hostel =function(){returnRoon;};}//Usevarhotel =NewHotel (' Guyojiu ', 23);

Arrays are also objects

JavaScript Learning Notes