Error in eval()

[surendragalwa11]

2+-3 or 2/3 and these kind of expressions are causing error in eval()*

import React, { Component } from 'react';
import update from 'immutability-helper';
import math from 'mathjs';
import './App.css';
import Display from './Display';
import Button from './Button';
import Buttons from './Buttons';

class App extends Component
{
  constructor()
  {
    super();
    this.state={
           operations: []
    };
  }

  calculateOperations = () => {
    var result = this.state.operations.join('');
    if(result)
    {
      result = String(math.eval(result));
      this.setState({ operations : [result] });
    }
    
  }

  handleClick = e => {
    var value = e.target.getAttribute('data-value');
    switch (value)
    {
      case 'clear': this.setState({ operations: []});  break;
      case 'equal': this.calculateOperations();  break;
      default: var newOperations = update(this.state.operations, {$push: [value]});
               this.setState({operations: newOperations}); break;
    }
  }

  render()
  {
    return (
      <div className="App">
        <Display data={this.state.operations} />
        <Buttons>
          <Button onClick={this.handleClick} label="C" value="clear" />
          <Button onClick={this.handleClick} label="7" value="7" />
          <Button onClick={this.handleClick} label="4" value="4" />
          <Button onClick={this.handleClick} label="1" value="1" />
          <Button onClick={this.handleClick} label="0" value="0" />
          
          <Button onClick={this.handleClick} label="/" value="/" />
          <Button onClick={this.handleClick} label="8" value="8" />
          <Button onClick={this.handleClick} label="5" value="5" />
          <Button onClick={this.handleClick} label="2" value="2" />
          <Button onClick={this.handleClick} label="." value="." />
          
          <Button onClick={this.handleClick} label="x" value="*" />
          <Button onClick={this.handleClick} label="9" value="9" />
          <Button onClick={this.handleClick} label="6" value="6" />
          <Button onClick={this.handleClick} label="3" value="3" />
          <Button label="" value="null" />
          
          <Button onClick={this.handleClick} label="-" value="-" />
          <Button onClick={this.handleClick} label="+" size="2" value="+" />
          <Button onClick={this.handleClick} label="=" size="2" value="equal" />
        </Buttons>
      </div>
    );
  }
}

export default App;