JS Basic Learning materials _ basic knowledge

1, prevent the browser does not support JS problems can be handled JS code like this
<script type= "Text/javascript" >
<!--
document.write ("Hello world!");
-->
</script>
2, JS placement location:
Header: Make sure that the script has been loaded when it is invoked
Body: Called when the page is loaded
External JS file: No <script> tags included
Usage: <script src = "xxx.js" >.....</sceipt>
3, Notes
Single line://
Multiple lines:/*.....*/
4, = = = equal sign equals the same type and value
5, three kinds of cue boxes
Warning: Alert ("alert");
Confirmation: Confirm ("confirm");
Hint: prompt ("prompt", "default value");
6. In Declaration
For (variable in object)
{
Executing code here
}
7, Regular expression
Test () Method: Retrieves the specified value in the string, or False if there is a return true
var patt1=new RegExp ("E");
document.write (Patt1.test ("The best things in life are Free");
EXEC () Method: Retrieves the specified value in the character, or returns null if there is a value found returned
var patt1=new RegExp ("E");
document.write (Patt1.exec ("The best things in life are Free");
Compile () method: Used to change the retrieval mode and add delete second parameter