Determine the number of key-value pair

Given an object, return the number of key-value pair.

Sample Code:

function countProp(obj) {
// Enter your logic here...
}

Examples:

Input: {key1:'value',key2:'value'}
Output: 2
Explanation: The object has two key-value pair.

Input: {}
Output: 0
Explanation: There are no key-value pairs in Object.