The seventh training assignment

1. Built-in objects

argument Defined only inside the function , Save the arguments of the function

Array Array objects

date Date object , Used to create and obtain objects

math Mathematical objects

string String object , Provides a series of operations on strings

1.2string

charAt(idx) Returns the character at the specified location

indexof Returns the specified string position , From left to right , Cannot find return one

substring Returns the specified string m Position start , take n Characters , If parameters N Omit , It means getting the end of the string

1.3math

math.random() random number

math.ceil Rounding up , Greater than the maximum integer

1.4date

getfullyear() year

getmonth() month

getdate() Japan

gethour() when

getminute() branch

getseconds() second

explain ：

getmonth() month ： Time to get 0~11

setmonth(): Time set 0~11

2. object

The object is javascript Core concept of , It is also the most important data type .javascript All data types of can be regarded as objects .javascript Provide multiple built-in objects . Objects are special data types with properties and methods .

{

key ： value .

key 2： value 2.

}

2.1 Object creation

js Create custom objects , There are three main ways ： Literal form creation , adopt new object objects creating , adopt object Object's create Method to create an object

1. brief introduction

javascript Is an object-oriented capability , Interpretive programming language . A little bit more specific , It is an object driven and relatively secure client segment scripting language , His main purpose is , Verify the data sent to the server , increase wed Interaction , Enhance user experience

1.1.1 object

Object is plus javascript Core concept of , It is also the most important data model ,javascript All of the data can be treated as objects ,javascript Provide various internal service objects , Objects are special data types with properties and methods , In short , The object , It's an unordered set of data , It consists of several straight pairs , adopt javascript We can create our own objects ,javascript The song of this key value pair with opposite satisfaction is what we call json, I'll see you a lot later , The great json object

1.1.2 Serialization and deserialization of objects

serialize js Object serialization string , Deserialization means that the string is deserialized to js object ,js By calling json Method , You can sequence objects into strings , You can also deserialize strings into objects

1.1.3this

this yes javascript A keyword of language , It represents the function runtime , Automatically generate an internal object , Can only be used inside a function , As the function is used in different situations , Similar words will also change , But there is a general principle , This refers to the object that calls the function

2.JS event

2.1 event

Event is javascript Use the beating heart to interact with the page , When we interact with wed Some types of interactive events happen when the page is in progress , The event may be that the user clicks the mouse over certain elements or presses certain keys on the keyboard , It could be WED What happens in the browser , For example, a certain wed The page is loaded or the user scrolls to create a fire to change the window size , By using JavaScript You can monitor the occurrence of special time .

2.2 effect

1. Data entered by the user

2. Increase the dynamic effect of the page

3. Increase user experience

2.3 Several nouns of events
Event source ： Who touched the event

Time name ： What event triggered

Event monitoring ： Who monitors this event

Event handling ： What should I do when it happens

2.3 Event flow and event model

We all have a specific event source , For the time being, consider the event source as html Some element of , Then be a html When the element produces an event , This event will propagate in a specific order between the element node and the root node , All nodes passing through will be affected by this event. This propagation process is called dom Flow of events ,

There are two types of chronological order , Event capture and event bubbling , Bubbling and trapping are actually different representations of event flow , The reason for these two is love one and netscape Two big companies have completely different concepts of event flow ,ie Events are events bubbling ,netscape The event stream of is the event capture stream

3.1html Event handler

Each event supported by an element can use a with the same name as the corresponding event handler html Characteristics to develop , The value of this feature should be able to execute javascript Code , There are some disadvantages in doing so , for example , Too high coupling can also cause time difference , And on different browsers , May have different effects
3.2domo Event handler

adopt javascript The traditional way to specify event handlers , Is to assign a function to a time handler property , This approach is supported by all modern browsers , This method first requires a reference to the object to be operated , Every element has its own thing , Build handler properties , These attributes are usually all recreational , Then set the value of this attribute to a function , You can specify the world handler