Tutorial Detect Javascript On/Off, With Notification

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<script type="text/javascript">
   document.write("Welcome, you have Javascript on.")
</script>

<noscript>JavaScript is off. Please enable to view full site.</noscript>

If JavaScript is on the user gets a welcome message. If off, the user is instructed to turn it on.

Tutorial Detect Internet Explorer

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<script type="text/javascript">

if (/MSIE (\d+\.\d+);/.test(navigator.userAgent)) { //test for MSIE x.x;
 var ieversion=new Number(RegExp.$1) // capture x.x portion and store as a number
 if (ieversion>=8)
  document.write("You're using IE8 or above")
 else if (ieversion>=7)
  document.write("You're using IE7.x")
 else if (ieversion>=6)
  document.write("You're using IE6.x")
 else if (ieversion>=5)
  document.write("You're using IE5.x")
}
else
 document.write("n/a")

</script>

Reference

Tutorial Default Arguments for Functions

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// Combiner of passed arguments and defaults (usable with any function)
Object.prototype.combine = function(_args){
  for(var i in this) {
    if(typeof _args[i] == "undefined") {
      _args[i] = this[i];
    }
  }
};

// Specific example function with defaults
function feedTheCat(args){
  var defaults = {
      'morning' : "nothing",
      'noon'    : "pork",
      'nite'    : "mouse"
  };
  defaults.combine(args);
}

// USAGE: only passing 2 of 3 arguments
feedTheCat({
  'morning': "milk", 
  'nite': "kitekat"
}); 

// Values would be: milk | pork | kitekat

Reference URL

Tutorial Current Page with JavaScript

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This is like a replacement for PHP's SCRIPT_NAME with JavaScript.

location.href.split('/').pop();

For example with this URL:

http://css-tricks.com/examples/ScriptName/index.php

This code:

document.write( location.href.split('/').pop() );

Would write to the page: "index.php"

Reference URL

Tutorial CSS for when JavaScript is Enabled

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document.documentElement.className = "js"

This adds a class to the root <html>, so you could (for example) do something like hide a <div> only when JavaScript is enabled.

.js div#id { display: none; }

Tutorial Cookie Getter/Setter

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/**
 * Gets or sets cookies
 * @param name
 * @param value (null to delete or undefined to get)
 * @param options (domain, expire (in days))
 * @return value or true
 */
_.cookie = function(name, value, options)
{
    if (typeof value === "undefined") {
        var n, v,
            cookies = document.cookie.split(";");
        for (var i = 0; i < cookies.length; i++) {
            n = $.trim(cookies[i].substr(0,cookies[i].indexOf("=")));
            v = cookies[i].substr(cookies[i].indexOf("=")+1);
            if (n === name){
                return unescape(v);
            }
        }
    } else {
        options = options || {};
        if (!value) {
            value = "";
            options.expires = -365;
        } else {
            value = escape(value);
        }
        if (options.expires) {
            var d = new Date();
            d.setDate(d.getDate() + options.expires);
            value += "; expires=" + d.toUTCString();
        }
        if (options.domain) {
            value += "; domain=" + options.domain;
        }
        if (options.path) {
            value += "; path=" + options.path;
        }
        document.cookie = name + "=" + value;
    }
};

Reference URL

Tutorial Comments in JavaScript

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function doSomething() {

    /*
           This code by Chris Coyier
    */

    var i = 0;    // counter to be used later;

}

Comments in JavaScript can be between /* */ markings (useful for multiple line comments) or after // markings (for single lines only).