Inexplicable JS Basic Learning!

JavaScript Basic components:

1,ECMASCRIPT:JS syntax criteria, basic variables, operators, functions, if statements, for statements, etc.

2,dom: Manipulate the element API on the Web page, such as the movement of the box, color change, carousel diagram, etc.

3,bom: API functionality in the Operations browser section

Alert statement:

1, pop up the warning box statement, mainly used to pop up the hint in the webpage.

Basic code:

<script type= "Text/javascript" >  alert (2345678) </script>

2, two ways of annotation;

1,/**/Multi-line comments

2,//Single-line comment

3, console output: Console.log ("")

4,prompt () Statement: User dialog box input.

　　

<script type= "Text/javascript" >  var a = prompt ("Hello! ")   //dialog box  Console.log (a)//  output </script>

5, the name of the variable is the same as Python, but the use of hump body more

Data type:

Type viewing mode: typeof

1,number Number Type:

var a = 1234;

Console.log (typeof a)

2,string: String

var str = "123"

Console.log (typeof str)

3,boolean: Boolean values similar to Python

4,null: Empty Object

5,undefined: Variable not defined

6, operators need to be aware that only = = = This is to determine whether the data type and value are exactly the same

About splicing thief his mother disgusting!!! As long as there is a str, mate + is stitching

7, digital type conversion, strong turn on the good!!

8, Process Control!

1,if,if-else,if-else If-else:

　　

var ji = 20;if (ji>10) {  console.log (JI)    }alert ("Baichi")
This is the simplest way to use only if it exists

var ji  = 20;if (ji>=20) {    console.log (' 2333 ')}else{    console.log (' JS is sb! ‘)}
Simple Application

if (true) {   //execute Operation}else if (true) {    //satisfies condition execution            }else if (true) {   //satisfies condition execution        }else{  //Satisfies condition execution}
is different from Python and needs to be added if to expand

2,&& and | | is equivalent to and and or python, so no explanation

3,switch need to focus on memory!

　

var sb = "js"    Swich (SB)//Condition {case    "JS":    console.log ("Awesome!") ") break    ;//need to be aware that you must break the case    " python ":    console.log (" You will die with a sense of logic ") break    , Case    " CSS ":    Console.log ("You're nuts!") ") Break    ;}

4,while cycle, basically the same, change is the condition and the loop body need to set up parentheses

5,do_while executes the do before executing the while loop.

6,for Cycle

<! DOCTYPE html>
　　
 Inexplicable JS Basic Learning!