JS Basics 1

First, JavaScript

• Different from Java
• There are three components
• Core (ECMAScript)
• Document Object Model (DOM)
• Browser object Model (BOM)

var is the prefix that defines the data before adding three, pop-up

• Alert () Pop-up window, display content
• Confirm () Displays a dialog box with the specified message (the contents of the confirm) and the OK and Cancel buttons
• Prompt (text, value);
• Action: Displays a dialog box to prompt the user for input
• Text: Display plain text in a dialog box (non-HTML-formatted text)
• Value: Default input text (can be empty)

Iv. external inductive <script type= "Text/javascript" src= "Xxx.js" ></script> Five for finding data type typeof, throw find Type a below

• Alert (typeof a);

VI. Basic Types

• Numeric only if the type is numeric
• String when double quotes are added
• True and False for Boolean types
• Empty type
• Object: Document

Vii. naming rules

• Case sensitive
• The first letter must be a letter, an underscore, or a dollar sign $
• Cannot contain spaces
• Cannot use canonical word
• A naming convention is typically preceded by a type

Eight, arithmetic symbols

• /division, a decimal point appears
• + for numeric values are added, for strings are stitching
• ！ It can be used to reverse the judgment condition.

Nine, conditional statement--IF statement

• If-else statements
• Other wording: Judging the condition? Expression 1: Expression 2;
• When the judgment condition is set, the expression 1 is executed, and the expression 2 is executed.

Ten, + + 、--

• i++ is only added after the call.
• The ++i is added before the call

XI. format

• Window.onload = function () {、、、}
• Function content is not executed until the full page has been scanned
• When doing projects, it is best to introduce external files behind the body
• var oshow = document.getElementById ("show"); Get
• Oshow.onclick = function () {、、、} Click event

12, Continue&&break

• Continue end Current loop
• Break ends the entire loop

JS Basics 1