_(Previous Post: [Part 2](/@jfollas/write-a-steemit-web-app-part-2-followers-and-following))_
# What is Voting Power?
Voting Power is a rate-limiting feature of Steem to help prevent abuse. Each vote cast reduces the user's voting power by 2% of their remaining pool. So, if someone (or a bot) goes wild and upvotes hundreds of posts, then each upvote is worth less than the previous one (eventually being worth nothing).

Voting power regenerates linearly over 5 days, or 20% per day. So, with HF19, most people have set a goal of only depleting 20% of their voting power per day so that it will regenerate to 100% within 24 hours. This means that they can vote 11 times (at 100% per vote - only worth noting for those with enough steem power to unlock the ability to choose how much each vote is worth):

#|Voting Power
----|----
(Start)|100.00%
Vote 1|98.0%
Vote 2|96.04%
Vote 3|94.12%
Vote 4|92.24%
Vote 5|90.40%
Vote 6|88.58%
Vote 7|86.81%
Vote 8|85.08%
Vote 9|83.37%
Vote 10|81.71%
**Vote 11**|**80.07%**

## Representing Voting Power in a Web App
When you fetch account information with Steem.js, such as with the `getAccounts()` function, you get a `voting_power` number in the account data object: `{ ..., voting_power: 9668, ... }`. However, if you keep refreshing, you will not see this number ever change on its own - even if it's been five days since the last vote. This value is only updated when a user casts a vote. 

_Note: A LOT of the Steem applications out there are guilty of just showing this value... so even if you are really at 100% voting power, the apps won't reflect that._

But, there is another value in the account data object that is also updated when a vote is cast: `{..., last_vote_time: "2017-07-03T01:12:15", ...}`. So, your web app must do the task of calculating the current voting power value given these two inputs.

The basic formula is to take the reported `voting_power` and add in how much should have been regenerated since the `last_vote_time`. The maximum result would be 100%.

## JavaScript Code
In the [first post](/@jfollas/write-a-steemit-web-app-part-1-hello-user) of this series, we used the following code in the naive way to represent the user's voting power:

```javascript
vm.$set(vm.userData, 'power', result[0].voting_power / 100)
```

<br/>To correct this, we must first figure out how many seconds have passed:

```javascript
let secondsago = (new Date - new Date(result[0].last_vote_time + "Z")) / 1000
```

<br/>Next, divide the `secondsago` by the number of seconds in 5 days (`432000`) in order to get a percentage of how much of the 5 days has elapsed. Multiply this by `10000` (100%) to calculate how much voting power has regenerated so far, and add to the `voting_power` value from the account object:

```javascript
let vpow = result[0].voting_power + (10000 * secondsago / 432000)
```

<br/>Now we can set the value in our viewmodel (taking care of formatting and ensuring that the max is 100%):

```javascript
vm.$set(vm.userData, 'power', Math.min(vpow / 100, 100).toFixed(2))
```

<br/>The whole thing together would look like:

```javascript
steem.api.getAccountsAsync([accountName])
  .then(function (result) {
    ...
    let secondsago = (new Date - new Date(result[0].last_vote_time + "Z")) / 1000
    let vpow = result[0].voting_power + (10000 * secondsago / 432000)
    vm.$set(vm.userData, 'power', Math.min(vpow / 100, 100).toFixed(2))  
    ...
  })
```

<br/>Improvements to this would be to periodically recalculate the value using a timer so that the user always sees their latest voting power (especially if they are waiting for it to tick over to 100%).

![javascriptlogo.png](https://steemitimages.com/DQmZBbDGvKqM8V46NHaXoT7nZvrXhHLtTysrhixRu8eS87g/javascriptlogo.png)

_(Next Post: [Part 4](/@jfollas/write-a-steemit-web-app-part-4-calculating-steem-power))_