WEB Authoring - Javascript: 2015

čtvrtek 3. prosince 2015

How to check if cookies are enabled

The navigator object has the attribute cookieEnabled that returns true if the cookies are enabled in the browser. Find a simple example bellow.

<HTML>
<HEAD>
  <SCRIPT>
    function checkCookies(){
    window.alert("Are cookies enabled? "+(navigator.cookieEnabled?"Yes":"No"));
    }
  </SCRIPT>
</HEAD>
<BODY>
  <BUTTON onclick="checkCookies()">Check cookies</BUTTON>
</BODY>
</HTML>

středa 2. prosince 2015

Periodical Call of Javascript Function using SetTimeout

The following example shows how to set up a periodical function call of JavaScript function inside an html page.


<html>
<head>

<script>
var imageRefs = ["pict1.png","pict2.png","pict3.png"];
var counter = 0;

(function changeImage(){
  
 image = document.getElementById("image1");
 if(image != null) {
   image.src = imageRefs[counter];
   counter = (counter + 1) % 3;
   }

 setTimeout(changeImage,2000);

})();
</script>

</head>
<body>

<img id="image1" src="pict1.png" />

</body>

</html>

Here is the working example:

Change picture on click

A following simple example shows how to write the html page with pictures that rotate on mouse click event.

<html>
<head>

<script>
function changeImageOnClick(){
    image=document.getElementById("image1");
    
        if(image.src.indexOf("pict1.png")<0)
            image.src="pict1.jpg";
        else
            image.src="pict2.jpg";
}
</script>
</head>
<body>

<img src="pict1.png" id="image1" onclick="changeImageOnClick()"/>

</body>

Here is the working example:

pondělí 30. listopadu 2015

Browser language - navigator.language versus navigator.languages

I tried a simple test using the following html to explore the language information provided by Chrome, Firefox and IE.

<html>
<head>
</head>
<body>
<script>
var browserLanguage = navigator.language;
var preferredLanguageList = navigator.languages;
window.alert("Browser Language: "+browserLanguage+"\n"+"Preferred Languages: "+preferredLanguageList);
</script>
</body>
<html>

The results follow:

Chrome Version 46.0

navigator.language - returns the browser language (set by Display Google Chrome in this language button in Settings / Language and input settings)
navigator.languages - returns the list of preferred languages in order set in the Languages box (Settings / Language and input settings)

Firefox Version 38.4

navigator.language - returns the first item of list of Languages in the Options / Content / Languages
navigator.languages - returns the list of all items of Languages in the Options / Content / Languages (in order set by the Languages box)

Internet Explorer 11.0

navigator.language - returns the current system locales from Window Regional Settings
navigator.languages - is undefined in IE, I have not find how to get the list of preferred languages from Javascript. The only way is to parse the Accept-Language header field of http request on the server side