# JavaScript Solution to Number of Recent Calls

Number of Recent Calls is one of the leetcode questions that tripped us up. (As you can see how many downvotes it has.š§) In the following blog, Iāll try to explain the problem and the example line by line to make it easier to understand.

Number of Recent Calls is one of the leetcode questions that tripped us up. (As you can see how many downvotes it has.š§) In the following blog, Iāll try to explain the problem and the example line by line to make it easier to understand.

Explanation of the question

Write a class `RecentCounter` to count recent requests.

The key point above is class, we need to implement a class, not a function.

It has only one method: `ping(int t)`, where _ t_ represents some time in milliseconds.

The class instance needs to have _**_ping_ method, which is a function that takes _t**, an integer in the range of `1 <= t <= 10^9_` , as an argument._

Return the number of `ping`s that have been made from 3000 milliseconds ago until now.

The _**_ping**_ method return value is an integer._

Any ping with time in `[t - 3000, t]` will count, including the current ping.

Any _ _previous t _ _that has been called, which is in the range of [current t-3000, _**_current t**], will be counted.

It is guaranteed that every call to `ping` uses a strictly larger value of `t` than before.

Each call of _**_ping_, the argument _t**_ increases, it forms an ascending integer list._

Example 1:

``````Input: inputs = ["RecentCounter","ping","ping","ping","ping"],
/*
first, we create a new RecentCounter object
obj = new RecentCounter()
then, we call ping four times with four different t
*/
inputs = [[],[1],[100],[3001],[3002]]
/*
obj.ping(1)
obj.ping(100)
obj.ping(3001)
obj.ping(3002)
*/
Output: [null,1,2,3,3]
/*
object initialized, ping is not called, no return value, null
obj.ping(1) should return 1
obj.ping(100) should return 2
obj.ping(3001) should return 3
obj.ping(3002) should return 3
*/``````

Note:

1. Each test case will have at most `10000` calls to `ping`.
2. Each test case will call `ping` with strictly increasing values of `t`.
3. Each call to ping will have `1 <= t <= 10^9`.

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