React calculator code: checking if a number already exists?

Is there anyway that I could check if a number already exists (and for instance, if there are more than one instance of a particular number, etc) in state in this code? I can´t figure out any, and I´ve tried all methods I could think of (Indexof, contains, etc).

const button1 = [{number: 'one', value: '1'},{number: 'two', value: '2'},{number: 'three', value: '3'},{number: 'divide', value: '/'}];

const button2 = [{number: 'four', value: '4'},{number: 'five', value: '5'},{number: 'six', value: '6'},{number: 'add', value: '+'}];

const button3 = [{number: 'seven', value: '7'},{number: 'eight', value: '8'},{number: 'nine', value: '9'},{number: 'subtract', value: '-'}];

const button4 = [{number: 'zero', value: '0'},{number: 'equals', value: '='},{number: 'multiply', value: '*'}];


  class Calculator extends Component {
  constructor(props) {
    super(props);
    this.state = { value: "0"};
    this.handleClick = this.handleClick.bind(this);
    this.handleDecimal=this.handleDecimal.bind(this);
  }


 handleClick(evt) {
    const id = evt.target.id;
    const result = evt.target.value;

switch(id) {
    case 'clear':
        this.setState({ value: "0"});
        break;
    case 'equals':
      this.setState(prevState => ({
        value: math.eval(this.state.value)
      }));
        break;

    default: this.setState(prevState => ({
        value: `${prevState.value}${result}`
          .replace(/([/+\-/*=])([/+\-*=])/g, "$2")
          .replace(/^0+(?=[1-9])/, "")
          .replace(/^0+(?=\.)/, "0")
          .replace(/^0+\B/, "")
          .replace(/\.+/g,".")
      })); 
}


}

handleDecimal(evt){
let result2=evt.target.value;
let value=this.state.value;
let decimalPosition=value.indexOf(result2);
let numbers=/[0-9]/g;
let numberSearch=value.search(numbers);

  
if(numberSearch>decimalPosition){
 this.setState({value:this.state.value + result2}); 
}



}


render() {
    return(
            <div id="container">
                <Display value={this.state.value} />
                <div>
  {button1.map((el, index) => <Button onClick={this.handleClick} key={el.index} id={el.number} value={el.value} />)}

                </div>
                <div>
 {button2.map((el, index)  => <Button onClick={this.handleClick} key={el.index} id={el.number} value={el.value} />)}
                </div>
                <div>
 {button3.map((el, index)  => <Button onClick={this.handleClick} key={el.index} id={el.number} value={el.value} />)}
                </div>
                <div>
 <Button onClick={this.handleDecimal} id="decimal" value={'.'}  />
{button4.map((el, index) => <Button onClick={this.handleClick} key={el.index} id={el.number} value={el.value} />)}
                </div>
                <div>
                <Button onClick={this.handleClick} id="clear" value={'clear'}  />
                </div>
            </div>
)

}

}