Hello guys! morning and welcome to this new tutorial post on JavaScript. In my last tutorial post i talked about JavaScript For Loop, so in this tutorial we are going to be discussing about another form of looping.
The for....in loop is used to loop through an object's properties. Due to the fact that we have not yet discussed object, you might not feel comfortable with this loop. But once you understand how objects behave in JavaScript, you will appreciate and discover the usefulness of this loop.
The for....in loop is used to loop through an object's properties. Due to the fact that we have not yet discussed object, you might not feel comfortable with this loop. But once you understand how objects behave in JavaScript, you will appreciate and discover the usefulness of this loop.
You can check out our tutorial post on: JavaScript Operators
Syntax
Below is the syntax of JavaScript for....in loop:
for (variablename in object) {
Statement or block to execute
}
Statement or block to execute
}
In each iteration, one property from object is assigned to variablename and this loop continues till all the properties of the object are exhausted.
Example
Try the following example to implement for....in loop. It prints the web browser's Navigator object.
You can also check out our tutorial post on: JavaScript Variables
<html>
<body>
<script type="text/javascript">
<!--
var aProperty;
document.write("Navigator Object Properties <br />");
for (aProperty in navigator) {
document.write(aProperty);
document.write("<br />");
}
document.write("Exiting from the loop! ");
//-->
</script>
</body>
</html>
<body>
<script type="text/javascript">
<!--
var aProperty;
document.write("Navigator Object Properties <br />");
for (aProperty in navigator) {
document.write(aProperty);
document.write("<br />");
}
document.write("Exiting from the loop! ");
//-->
</script>
</body>
</html>
Below is the output of the above example
Navigator Object Properties
ServiceWorker
WebkitPersistentStorage
WebkitTemporaryStorage
geolocation
doNotTrack
onLine
languages
language
userAgent
product
platform
appVersion
appName
appCodeName
hardwareConcurrency
maxTouchPoints
vendorSub
vendor
productSub
CookieEnabled
getStorageUpdates
getGamepads
webkitGetUserMedia
vibrate
getBattery
sendBeacon
registerProtocolHandler
UnregisterProtocolHandler
Exiting from the loop!
ServiceWorker
WebkitPersistentStorage
WebkitTemporaryStorage
geolocation
doNotTrack
onLine
languages
language
userAgent
product
platform
appVersion
appName
appCodeName
hardwareConcurrency
maxTouchPoints
vendorSub
vendor
productSub
CookieEnabled
getStorageUpdates
getGamepads
webkitGetUserMedia
vibrate
getBattery
sendBeacon
registerProtocolHandler
UnregisterProtocolHandler
Exiting from the loop!
Alright guys we have come to the end of this tutorial post on JavaScript for....in loop. Follow us on our various social media handles to stay updated. Also feel free to to drop your questions in the comment box below, bye for now.