JavaScript for…in loop
The for…in loop is used to loop through an object’s properties. As we have not discussed Objects yet, you may not feel comfortable with this loop. But once you understand how objects behave in JavaScript, you will find this loop very useful.
Syntax
for (variablename in object){ statement or block to execute }
In each iteration, one property from object is assigned to variable name 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.
<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> <p>Set the variable to different object and then try...</p> </body> </html>
Output
Navigator Object Properties serviceWorker webkitPersistentStorage webkitTemporaryStorage geolocation doNotTrack onLine languages language userAgent product platform appVersion appName appCodeName hardwareConcurrency maxTouchPoints vendorSub vendor productSub cookieEnabled mimeTypes plugins javaEnabled getStorageUpdates getGamepads webkitGetUserMedia vibrate getBattery sendBeacon registerProtocolHandler unregisterProtocolHandler Exiting from the loop! Set the variable to different object and then try...
