window.onerror=function(msg, url, linenumber){
 var logerror='Error message: ' + msg + '. Url: ' + url + 'Line Number: ' + linenumber
 alert(logerror)
 return true
}

See "The onerror event of the window object" for full details.

window.onload=function(){
 runsomefunction()
}

The limitation with the above approach is that multiple calls to window.onload on the same page causes all but the last one to be adopted, with each proceeding call overwritten by the one following it. On a page with multiple JavaScripts, this is more likely than not to happen. To overcome this, you can invoke the onload event handler using the DOM methods element.addEventListener() and its counterpart element.attachEvent() in IE. Event handlers defined in this manner will not get overwritten by their counterparts, but instead queued.

window.onscroll=function(){
 var scrollY=window.pageYOffset || document.body.scrollTop
 document.title=scrollY
}

window.onbeforeunload=function(e){
 e.returnValue="Any return string here forces a dialog to appear when user leaves this page"
}

window.location="http://www.google.com" //prompt is invoked

<iframe src="http://google.com"></iframe>
<iframe src="http://yahoo.com"></iframe>

<script type="text/javascript">

for (var i=0; i<frames.length; i++){
 frames[i].location="about:blank"
}

</script>

If the current page is contained in a frame itself and you wish to access another sibling frame, navigate up towards the topmost frameset document first using the parent property of window, for example:

parent.frames[0] //access first frame within parent frameset.

- Supported in: Firefox/Opera/Safari, but NOT IE.

Note: IE equivalents are "document.body.clientWidth" and "document.body.clientHeight"

- Supported in: Firefox/Opera/Safari, but NOT IE.

- Supported in: Firefox/Opera/Safari, but NOT IE.

Note: IE+ equivalents are "document.body.scrollLeft" and "document.body.scrollTop"

- Supported in: Firefox/Opera/Safari, but NOT IE.

Note: IE+ equivalents are "window.screenLeft" and "window.screenTop"

- IE only properties

- IE10+, FF11+, Chrome and Safari 6+

window.cancelAnimationFrame = window.cancelAnimationFrame
                              || window.mozCancelAnimationFrame
                              || function(requestID){clearTimeout(requestID)} //fall back to clearing a setTimeout requestID

Note: Older versions of Mozilla supported a prefixed version of cancelAnimationFrame(). All other relevant browsers starting supporting the unprefixed version from the beginning.

var yourstate=window.confirm("Are you sure you are ok?")
if (yourstate) //Boolean variable. Sets to true if user pressed "OK" versus "Cancel."
 window.alert("Good!")

- Firefox only property

- Firefox only property

Demo: Open Window

<script type="text/javascript">

function centeropen(url, winwidth, winheight){
 var centerwin=window.open(url, "", "toolbar=1, resize=1, scrollbars=1, status=1")
 centerwin.resizeTo(winwidth, winheight)
 centerwin.moveTo(screen.width/2-winwidth/2, screen.height/2-winheight/2) //center window on user's screen
}

</script>


<a href="#" onClick="centeropen('about:blank', 800, 650); return false">Open Window</a>

window.open("http://www.dynamicdrive.com", "", "width=800px, height=600px, resizable")

When defining the features (3rd parameter), separate each feature with a comma (,).

Restriction: In IE, an exception is thrown if you try to open a window containing a page from another domain and then try to manipulate that window. For example:

var mywin=window.open("http://www.notcurrentdomain.com", "", "width=800px, height=600px, resizable")
mywin.moveTo(0, 0) //Not allowed in IE: an exception is thrown.

This restriction does not apply in other browsers.

var yourname=window.prompt("please enter your name")
 alert(yourname)

- IE10+, FF11+, Chrome and Safari 6+

window.requestAnimationFrame = window.requestAnimationFrame
                               || window.mozRequestAnimationFrame
                               || window.webkitRequestAnimationFrame
                               || window.msRequestAnimationFrame
                               || function(f){return setTimeout(f, 1000/60)} //fall back method, run roughly 60 times per second

When requestAnimationFrame is called recursively, such as inside the function we pass into it, it behaves a lot like setInterval, except it repeats itself not based on the user defined interval, but again, at every next available screen repaint. Based on the typical screen refresh rate of 60 frames per second, a recursively called requestAnimationFrame would then be executed around 60 times per second.

requestAnimationFrame is an attractive replacement to setInterval for animating objects on the screen frame by frame, as it intelligently decides when to repeat itself based on the screen's readiness to repaint the screen. With setInterval, the user defined interval becomes meaningless, even counter efficient as constant changes in available system resources lead to frame skipping and layout thrashing.

requestAnimationFrame returns an unique ID you can use to cancel the next operation, using cancelAnimationFrame(ID).

The callback function entered into requestAnimationFrame(func) carries a single timestamp parameter that contains the current time in the form of milliseconds when the method was invoked. The following uses requestAnimationFrame to animate a DIV across the screen for the desired distance over the desired duration:

var myblock = document.getElementById("square")

var starttime = 0

function moveit(timestamp, el, dist, duration){
 if (typeof timestamp == 'undefined'){ //if  browsers don't support requestAnimationFrame, generate our own timestamp
  var timestamp = new Date().getTime()
 }
 if (starttime === 0){ //first time running requestAnimationFrame?
  starttime = timestamp
 }
 var runtime = timestamp - starttime
 var progress = runtime / duration
 progress = Math.min(progress, 1)
 el.style.left = (dist * progress).toFixed(2) + 'px'
 if (runtime < duration){ // if duration not met yet
  requestAnimationFrame(function(timestamp){ // call requestAnimationFrame again with parameters
   moveit(timestamp, el, dist, duration)
  })
 }
}

requestAnimationFrame(function(timestamp){
 moveit(timestamp, myblock, 400, 1000) // 400px over 1 second
})

Demo:

window.resizeTo(screen.availWidth, screen.availHeight) //see also the screen object

setInterval(myfunction, 5000) //function reference

var timer=setInterval("document.title='Current Second: ' + new Date().getSeconds()", 1000) //statements should be surrounded in quotes)

If you need to repeated call a function that accepts parameters, put that function inside an anonymous function:

setInterval(function(){myfunction(param)}, 5000)