Uncaught TypeError: Cannot read property 'strikes' of undefined at timerTriker (APP3.js:19)

import React from 'react';

class LightCounter extends React.Component{

constructor(props){

super(props);

this.state={

strikes:0

}

}

getInitialState(){

return {

strikes:0

}

}

timerTriker(){

this.setState({

strikes:this.state.strikes+100

})

}

componentDidMount(){

setInterval(this.timerTriker,1000)

}

render(){

return (

<div>

<h1>{this.state.strikes}</h1>

</div>

)

}

}

class LightCounterDisplay extends React.Component{

render(){

var divStyle ={

width:250,

textAlign:"center",

backgroundColor:"black",

padding:40,

color:"#999",

fontFamily:"sans-serif",

borderRadius:10

}

return (

<div style= {divStyle}>

<LightCounter />

</div>

)

}

}

export default LightCounterDisplay