2017-3-28 JavaScript Basics, syntax

Front Three Musketeers:

html+css+js(HTML determines what is on the page, CSS determines how things are placed, JS determines the function of things)

JS Definition:

JS is a scripting language that requires a host file, and its host file is an HTML file.

js function:Perform data operations
Control some features of the browser
Control elements
+ Properties
+ Style
+ Content

Reference Location:
Inline JS:You can place it anywhere in the HTML file:HeadInsideBobyInsideIt's all right behind you. It is recommended to write the JS code at the bottom of the page.
<script type= "Text/javascript" ></script>
External JS:Write the JS code to a file at the end of the. js, and then refer the file to the HTML file.
Embedded JS:Wait until the event.

three common dialog boxes:  1, alert (); Warning dialog box. The function is: Pop up a warning dialog box, for example: Alert ("error occurred");

2, confirm (); Determines the dialog box. The function is: Pop Up an optional OK dialog box, click OK, it returns true; Click Cancel to return False, the available variables to receive;

For example: Confirm ("OK to exit?") ");

3, prompt (); Enter the dialog box. The function is to pop up a dialog box that allows you to enter content. For example: Prompt ("Enter a number in the bar", "can only be a number Oh");

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JS Syntax:

1. Basic Data type: string, Decimal, Integer, Time Date, Boolean, etc.

2, variables: All types of variables are defined by VAR.

3, type conversion: automatic conversion and casting, generally with cast. parseint;parsefloat;

Determine if it is a valid number type:IsNaN (); If yes, returns False if not, returns True.

4, Operator: math Operator: +-*/% + +--;

Relational operators: = = = = >= <= > <;

Logical operator:&& | | ！;

Other operators: + = = *=/=%=?:;

5, statements: divided into sequential statements, branch statements, circular statements; (usage with C #)

6. Array:

definition of the array:var a=new array (); Its length is dynamic, which can be placed in any type of element;

Assignment of array elements:a[0]=123; a[1]= "Hello";

Array value:a[i];

Array properties:a.length; number of array elements, length.

method:a.sort (); Sort the array, sorted by the first character. A.reverse (); Flip an array

7. Function:

function Four elements: input, output, function name, function body

define functions:functionA (formal parameter) {function body} function return value can be var type or return value

function Call: A (formal parameter)

2017-3-28 JavaScript Basics, syntax