# conversion to arrow function and filter
```javascript=
import React from 'react';
class DaysInMonth extends React.Component{
constructor(props){
super(props);
this.state = {
monthList:['january', 'febuary', 'March', 'April', 'May', 'June', 'July', 'Auguest', 'September', 'octtober', 'November', 'December'],
year:2020,
day31: [],
day30: [],
day28: []
}
this.handlerDay31 = this.handlerDay31.bind(this);
this.handlerDay30 = this.handlerDay30.bind(this);
this.handlerDay28 = this.handlerDay28.bind(this);
}
handlerDay31(){
const months = this.state.monthList;
months.forEach((monthName, index) => {
const days = new Date(this.state.year, index + 1, 0).getDate();
if (days === 31) {
this.setState((prevState) => ({
day31: [...prevState.day31, monthName]
}))
}
})
}
handlerDay30() {
const months = this.state.monthList;
months.forEach((value, index) => {
const days = new Date(this.state.year, index + 1, 0).getDate();
if (days === 30) {
this.setState((prevState) => ({
day30: [...prevState.day30, value]
}))
}
})
}
handlerDay28() {
const months = this.state.monthList;
months.forEach((value, index) => {
const days = new Date(this.state.year, index + 1, 0).getDate();
if (days === 29 || days === 28) {
this.setState((prevState) => ({
day28: [...prevState.day28, value]
}))
}
})
}
render(){
return <div className="wrapper">
<div className="mLR10 dIB">
<ul>{this.state.day31.map((month) => <li>{ month }</li>)}</ul>
<button onClick={this.handlerDay31}>31 Days Months</button>
</div>
<div className="mLR10 dIB">
<div>{this.state.day30.map((month) => <li>{ month }</li>)}</div>
<button onClick={this.handlerDay30}>30 Days Months</button>
</div>
<div className="mLR10 dIB">
<div>{this.state.day28.map((month) => (<li>{ month }</li>))}</div>
<button onClick={this.handlerDay28}>28/29 Days Months</button>
</div>
</div>
}
}
ReactDOM.render(<DaysInMonth />, document.querySelector("#mountNode"))
```