The for...in loop is used to loop through an object's properties.
Syntax
Here’s the syntax −
for (variablename in object){
statement or block to execute
}Example
Try the following example to implement ‘for-in’ loop. It prints the web browser’s Navigator object
Live Demo
<html>
<body>
<script>
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>