The key could be any object, but it must be an especific one when is called.
if it is a String, cant be Object or Other class
<!DOCTYPE html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.29/browser.js"></script>
<script type="text/babel">
var course = new Map();
course.set('react', {description: 'ui'});
course.set('jest', {description: 'testing'});
console.log(course);
console.log(course.react);
console.log(course.get('react'));
var details = new Map([
[new Date(), 'today'],
['items', [1, 2]]
]);
console.log(details.size);
details.forEach(function(item) {
console.log(item);
});
</script>
<title>Maps</title>
</head>
<body>
</body>
</html>Output:
