Google Chrome does not support plug-ins, there is Firebug-like too already available built within Google Chrome. That is called “Inspect element” just right click on page anywhere and click on “Inspect element” menu command. It will open a new panel like firebug. It works well for CSS debugging and you can change CSS in real time like firebug but JavaScript debugging is not very good supported.
Here is the small JavaScript example that tells how you can use setTimeout() to auto refresh page content. You can utilize this script in games site or stock sites or anywhere you can think of.
PHPMIND – Javascript Tutorials
JavaScript Auto Refresh Page
This code will refresh you page in 6 seconds. We have used OnLoad() Event function to call our function.
Note : Please don’t use a lot of auto refresh page because it is kind of annoying and your sever bandwidth will be decreasing, one way you are increasing hits to server.
To include multiple js files in page is bad in terms of http request. Yslow Yahoo! tool can give you bad grade. Grade F on making more HTTP requests.
Apart from that page loading time increases and page does not looks clean.
Combined files are a way to reduce the number of HTTP requests by combining all scripts into a single script, and similarly combining all CSS into a single stylesheet.
Including multiple .js file in one external file has several advantages.
1. Less HTTP request.
2. If cashing is on page lode faster.
3. Page looks clean.
Use this code to add as much as files as you want.
document.write('');
document.write('');
document.write('');
document.write('');
To change the image using OnClick function i have found 2 ways.
1. Using jQuery.
2. Normal JavaScript.
Lets look one by one.
second by using simple JavaScript. I suggest not you use direct JavaScript call function. Good PHP Technology companies are not using like this.
Here is a self submitting form I wrote for a php form. Its simple, clean, and it works flawlessly.
As shown in the following table, you can use these JavaScript statements in your own code to create and modify variables in your JavaScript functions.
| Element | Description |
|---|---|
| var myVar = 0; | Creates a variable with given starting value. Type is determined dynamically. |
| stringVar = prompt(“message”) | Sends message to user in a dialog box, retrieves text input from user and stores it in stringVar. |
| stringVar.length | Returns the length (in characters) of stringVar. |
| stringVar.toUpperCase(), stringVar.toLowerCase() | Converts stringVar to upper- or lowercase. |
| stringVar.substring() | Returns a specified subset of stringVar. |
| stringVar.indexOf() | Returns location of a substring in stringVar (or -1). |
| parseInt() | Converts string to int. |
| parseFloat() | Converts string to float. |
| toString() | Converts any variable to string. |
| eval() | Evaluates string as JavaScript code. |
| Math.ceil() | Converts any number to integer by rounding up. |
| Math.floor() | Converts any number to integer by rounding down. |
| Math.round() | Converts any number to integer by standard rounding algorithm. |
| Math.random() | Returns random float between 0 and 1. |
JavaScript programmers commonly use the commands shown in the following table for controlling dialog-based input and output in programs to be used on the Web.
| Element | Description |
|---|---|
| alert(“message”); | Creates a popup dialog containing “message.” |
| stringVar = prompt(“message”) | Send message to user in a dialog box, retrieve text input from user and store it in stringVar. |
Look to the following table for JavaScript control structures you can use in your program code to add branching and looping behavior to your JavaScript programs.
| Element | Description |
|---|---|
| if (condition){ // content } else { // more content } // end if |
Executes content only if condition is true.
Optional else clause occurs if condition |
| switch (expression)
case: value; //code break; default: //code |
Compares expression against one or more values. If expression is equal to value, runs corresponding code. Default clause catches any uncaught values. |
| for(i = 0; i < count; i++)
//code } // end for |
Repeats code i times. |
| While (condition){
//code } // end while |
Repeats code as long as condition is true. |
| Function fnName(paramaters) {
//code } // end function |
Defines a function named fnName and sends it parameters. All code inside the function will execute when the function is called. |
JavaScript uses comparison operators inside conditions to make numeric or alphabetical comparisons of variables to other variables or values. Using these operators, you can determine whether a variable is greater than, less than, or equal to another variable or value. You can also use combinations of these comparison operators.
| Name | Operator | Example | Notes |
|---|---|---|---|
| Equality | == | (x==3) | Works with all variable types, including strings. |
| Not equal | != | (x != 3) | True if values are not equal. |
| Less than | < | (x < 3) | Numeric or alphabetical comparison. |
| Greater than | > | (x > 3) | Numeric or alphabetical comparison. |
| Less than or equal to | <= | (x <= 3) | Numeric or alphabetical comparison. |
| Greater than or equal to | >= | (x >= 3) | Numeric or alphabetical comparison. |
JavaScript allows you to put together code lines to create functions and variables to create arrays. You can put functions and variables together to create objects.
| Element | Description |
| function fnName(parameters) { //code } // end function |
Defines a function named fnName and sends it parameters. All code inside function will execute when the function is called. |
| var myArray = new Array(“a”, “b”, “c”); |
Creates an array. Elements can be any type (even mixed types). |
| Var myJSON = {
“name”: “title”: } |
Creates a JSON object. Each element has a name/value pair, and can contain anything, including an array (with square braces) another JSON object, or a function. |
| Var person = new Object();
Person.name = |
Creates an object. You can add ordinary variables (which become properties) or functions (which become methods). |
The Document Object Model methods shown in the following table offer you a great way to access and modify your Web pages through your JavaScript code.
| Element | Description |
| myElement = document.getElementById(“name”); |
Gets an element from the page with the specified ID and copies a reference to that element to the variable myElement. |
| myElement.innerHTML = “value” |
Changes the value of the element to “value”. |
| document.onkeydown = keyListener | When a key is pressed, a function called keyListener is automatically activated. |
| document.onmousemove = mouseListener |
When the mouse is moved, a function called mouseListener is automatically activated. |
| setInterval(function, ms); | Runs function each ms milliseconds. |
| myArray = document.getElementByName(“name”) |
Returns an array of objects with the current name (frequently used with radio buttons). |