Uncaught TypeError: Cannot read property ‘push’ of undefined (React-Router-Dom)

In order to make use of history in the App component use it with withRouter. You need to make use of withRouter only when your component is not receiving the Router props,

This may happen in cases when your component is a nested child of a component rendered by the Router or you haven’t passed the Router props to it or when the component is not linked to the Router at all and is rendered as a separate component from the Routes.

import React from 'react';
import { Route , withRouter} from 'react-router-dom';
import Dashboard from './Dashboard';
import Bldgs from './Bldgs';

var selectedTab;

class App extends React.Component {
  constructor(props) {
    super(props);
    this.handleClick = this.handleClick.bind(this);
    selectedTab = 0;
  }

  handleClick(value) {
    selectedTab = value;
    // console.log(selectedTab);
    this.props.history.push('/Bldgs');
    // console.log(this.props);
  }

  render() {
    var _this = this;

    return (
      <div>
        <Route exact path="https://stackoverflow.com/" render={(props) => <Dashboard {...props} handleClick={_this.handleClick} />} />
        <Route path="/Bldgs" component={Bldgs} curTab={selectedTab} />
      </div>
    );
  }
}

export default withRouter(App);

Documentation on withRouter