Getting Started with JavaScript (i)

Part of JavaScript

1. ECMAScript: It's the core of JavaScript (syntax, variables, data types, statements, functions ...)
2. DOM: (Document Object model) documents objects
3. BOM: (Brower object model) browser objects

The syntax of JavaScript

1. Case sensitive;
2. Weak type;
3. Comments are the same as Java;
4. define variables using Var;

Data types for JavaScript

1. Raw data type: String, number, Boolean, null, undefined
2. Application data type: Array, Boolean, Date, Math, number, String, reqexp

The JavaScript operator

1. = =: It will be converted automatically when making comparisons.
2. = = =: It does not convert automatically when making comparisons.
3. Other operators are basically consistent with Java

JavaScript gets element content

1. Get element: document.getElementById ("id name");

2. Gets the value inside the element: document.getElementById ("ID name"). Value;

The output of JavaScript

1. Warning Box: Alert ("string");
2. Writes to the location specified by the page: InnerHTML ("Write content");
3. Write content to page: document.write ("Write content");

Form submission events in javascript: onsubmit

Example 1: A simple registration form check

HTML code <form action= "#" method= "Get" name= "RegForm" onsubmit= "return Checkform ()" > <table border= "1px" width= "750px" height= "400px" align= "center" cellpadding= "0px" cellspacing= "0px" bgcolor= "white "> <tr height= "40px" > <TD colspan= "2" > <font size= "4" > member Registration </font> &nbsp;&nbsp;&nbsp; USER REGISTER </td> </tr> <tr> <td> User name </td> <td> <input type= "text" name= "user" size= "34px" id= "user"/> </td> </tr> <tr> <td> Password </td> <td> <input type= "password" name= "password" size= "34px" id= "password"/> </td> </tr> <tr> <td> Confirm Password </td> <td> <input type= "Password" name= "Repassword" size= "34px" id= "Repassword" ></input> </td> </tr> <tr> <td> Emaile </td> <td> <input type= "text" name= "email" size= "34px" id= "Eamil"/> </td> </tr> <tr> <td> Name </td> <td> <input type= "text" name= "username" size= "34px"/> </td> </tr> <tr> <td> Gender </td> <td> <input type= "Radio" name= "Sex" value= "male"/> Male <input type= "Radio" name= "Sex" value= "female"/> Female </td> </tr> <tr> <td> Date of birth </td> <td> <input type= "text" name= "Birthday" size= "34px"/> </td> </tr> <tr> <td> Verification Code </td> <td> <input type= "text" name= "Yzm"/> </td> </tr> <tr> <TD colspan= "2" > <input type= "Submit" value= "register"/> </td> </tr> </table> </form>

JavaScript code <script> Function checkform () { //alert ("AA"); /** Verify User name */ //1. Get user-entered data var uvalue = document.getElementById ("user"). Value; //alert (uvalue); If (uvalue== ") { //2. Error message Alert (" User name cannot be empty! "); return false; }   /* Check password */ var pValue = document.getElementById ("password"). Value; If (pvalue== ") { Alert (" Password cannot be empty! "); return false; }   /** Check Confirm password */ var rpvalue = document.getElementById ("Repassword"). Value; if (rpvalue!=pvalue) { alert ("Two times password input is inconsistent!"); return false; }   /* Check mailbox */ var evalue = document.getElementById ("Eamil"). Value; If (!/^ ([a-za-z0-9_-]) [email protected] ([a-za-z0-9_-]) + (. [ A-za-z0-9_-]) +/.test (evalue) { Alert ("The mailbox format is incorrect!"); return false; }   } </script>

Getting Started with JavaScript (i)