Shulou(Shulou.com)06/01 Report--

This article mainly explains "basic usage of html+css+javaScript". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn the basic usage of html+css+javaScript.

1. Definition and characteristics of JS

(1) briefly describe the characteristics of javaScript.

JavaScript is a literal scripting language, a dynamically typed, weakly typed, prototype-based language with built-in support for types.

(2) briefly describe the function of javaScript.

Html+css knowledge can have static pages, but no dynamic effect

Js can realize the verification of form data.

Switching of TAB menu

Switching of background pictures

Development of Js Mini Game

(3) Please list the advantages and disadvantages of javaScript

Advantages:

1. Script language

Scripting language is a simple program that is constructed by some ASCII characters

It can be written using any kind of text editor. Some programs

Languages (such as C, C++, Java, etc.) must be compiled to convert the source

The code is compiled into a binary executable file before it can be run, while

Scripting languages do not need to be compiled in advance, as long as there is a suitable one

The interpreter can be executed.

A scripting language is a programming language that is interpreted and executed by an interpreter in a web browser. Each time a program is run, the interpreter translates the program code into an executable format.

two。 Object-based language

Object-oriented has three characteristics (encapsulation, inheritance, polymorphism).

Usually "object-based" uses objects, but it is impossible to use existing object templates to generate new object types, that is to say, "object-based" has no inheritance characteristics. Without the probability of inheritance, there is no way to talk about polymorphism.

3. Event driven

An action that performs an action in a web page is called an Event, such as pressing the mouse, moving the window, selecting a menu, and so on. When the event occurs, it may cause the corresponding event response.

4. Simplicity

Variable types are weakly typed and do not use strict data types.

Var a dint bpene c afei 123b = "abc" aqumb

5. Security.

JavaScript cannot access the local hard disk, save data to the server, modify or delete network documents, and can only browse information or interact dynamically through a browser.

6. Cross-platform

JavaScript depends on the browser itself, independent of the operating platform

As long as the computer installs a browser that supports JavaScript (with a JavaScript interpreter), the JavaScript program will execute correctly

Disadvantages:

The degree to which various browsers support JavaScript is different, supporting and not fully supporting JavaScript. When browsing the same web page with javaScript script, the effect of the browser will be different, and sometimes it will not even be displayed.

2. Declaration and introduction of JS

(1) there are several ways to introduce javascript, how to write them respectively?

1. Two kinds

/ / Web page pop-up box

Var axi1

Var Aspir2

Alert (A)

two。

(2) can the introduction of javascript be written comprehensively? Please explain why.

No, an error will occur.

(3) the function of type= "text/javascript" attribute and charset= "UTF-8" attribute of javaScript tag

The second introduction method of js src: the path of the import file type: the type of the import file charset: character encoding

3. Variables in JS

(1) are variable names in JS case sensitive?

Distinguish

(2) can semicolons be omitted at the end of writing expressions in JS?

Sure

(3) Specification of variable names in JS

1. The name of the variable in js is the same as that of the identifier in java.

2. The variable name in Js can be repeated, but the name of the latter overrides the name value of the former.

3. It is OK at the end of Js even if there is no end of the branch, but it is not recommended to write in this way.

4. Data types in JS

Basic data type

Number (data of numeric type)

String (string type)

Boolean (Boolean data type)

Object (object type)

Special data types in Js

Undefined (undefined)

NaN (not a number) not a number

Null (empty object)

(1) what is the meaning of NAN data type in JS and how is it generated?

Not a number (not a number) forcibly converts string (containing non-numeric) types to number types

(2) what is the meaning of undefined data type in JS and how is it generated?

Undefined, just declared the object, not defined it

(3) var aura null; alert (type a) what pops up?

Null object

5. Operators in JS

(1) what is the difference between "=" and "=" in JS, as well as their respective functions?

"=": the equivalents first compare whether the two value types are equal.

If the type is not equal, it is strongly converted to number, and then judged. Equal returns true, unequal returns false.

"=": equivalents: compare whether two value types are equal

If the type is not equal, it will not be forced to return false directly.

(2) 5.2.2 Please print the following results respectively

Var f1 false; type: Boolean strong to number:0

Var f2 = "false"; type: object to number:NaN

Var f3: 0; Type: number

Var f4 = "0"; type: object to number:0

Alert (f1==f2); F

Alert (f1==f3); T

Alert (f1==f4); T

Alert (f2==f3); F

Alert (f2==f4); F

Alert (f3==f4); T

Alert (f1===f2); F

Alert (f1===f3); F

Alert (f1===f4); F

Alert (f2===f3); F

Alert (f2===f4); F

Alert (f3===f4); F

6. Control statements in JS

(1) what is the difference between if () {} and if () {} else if () {}.. else {}

If () {} has only one judgment.

If () {} else if () {}: refers to successive judgments

(2) are the variables in the for loop local?

No,

7. Learning functions in JS

(1) what are the ways in which functions are declared? Please explain the specific function.

Three kinds

Function name () {}

Var a=function () {}

Var a=new function () {}

Function demo (a _ r _ b) {

Alert (a + "" + b)

Return a

}

Var demo2=function () {

Alert (234)

Return 123

}

Var c=new Function ("alert ('234')")

(2) Please state the function of the function executor.

Convenient to call

8. Date and Math objects in JS

(1) Please name the common methods of Date object

Get the day of the current month

Date.getDate ()

Var v=date.getDay (); (1-6)

V=date.getFullYear (); / / get the four-digit year

V=date.getHours (); / / get hours (0-23)

V=date.getMonth (); / / get month (0-11)

V=date.getTime (); / / the number of milliseconds returned from 1970 to the present when getting the time

(2) Please describe the common methods of Math objects.

Var math=Math.random (); / / get the random number of 0-1 [0jue 1)

Math=Math.floor (Math.random () * 900,100)

9. String and Global in JS

(1) Please describe the common methods of String object

/ / intercept string

Var str= "I-is-Super-level-Sai-Ya-Man"

Console.log (str.charAt (3))

/ / intercept the specified number from the starting index

Console.log (str.substr (0Pol 2))

/ / intercepting characters between specified index numbers does not include 2

Console.log (str.substring (1pm 2))

/ / display the string as subscript

[xss_clean] ("wudiu" + str.sub ())

/ / replace the specified string

Console.log ("I am", "Sun Wuhan"))

Detach string

Console.log (str.split ("-")); / / get an array array

(2) Please describe the common methods of Global object

Var b = "var censor 1"; eval (b) parses the js code in the string

10. Array object Learning An in JS

(1) can array subscripts in JS be discontiguous?

It can be discontiguous, and the subscript that is not copied between them is replaced by empty.

(2) what does it mean by the number of var arr2=new Array parameters in the declaration of the array?

Weakly typed language, the sound is the same without declaration.

11. Array object Learning B in JS

(1) ask whether the length of the array in JS is variable.

No

(2) there are several ways to traverse arrays in JS, please list.

(3) Please list the common methods of arrays in JS.

Methods commonly used in / array

Function demo5 () {

Var arr= ["bjsxt", 123 new Date (), false]

/ / add one or more elements to the end of the array and return the first length

Var len=arr.push ("invincible", "sdfsdf")

/ / Delete and return the last element of the array

/ / arr.pop ()

/ / Delete and return the first element of the array

Arr.shift ()

/ / add one or more elements to the beginning of the array and return a new length

Arr.unshift ("shw")

/ / delete or modify the array

/ / the subscript that starts to be deleted and the number of deletions

Arr.splice (1 dint 2)

/ / added meaning added subscript deletes 0 added elements

Arr.splice (1, "Hello")

Console.log (arr)

12. Event Learning Event in JS

(1) Please list the common events

(2) what is the scenario in which onclick events and onchange events are used?

Onclick: can only be used on buttons (submit, empty, normal buttons)

Onchang: will be triggered when the content changes and is not focused

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