MyWebView.js

import React, { Component, PropTypes } from 'react';
import { WebView } from 'react-native';
import CookieManager from 'react-native-cookies';

export default class extends Component {
  static propTypes = {
    clearCookies: PropTypes.bool,
  };

  static defaultProps = {
    clearCookies: true,
  };

  constructor(props) {
    super(props);
    this.state = {
      url: null,
    };
  }

  componentWillMount() {
    if (this.props.clearCookies) {
      CookieManager.clearAll(() => {
        this.setState({url: this.props.url});
      });
    } else {
      this.setState({url: this.props.url});
    }
  }

  render() {
    return (
      <WebView
        {...this.props}
        source={{uri: this.state.url}}
        startInLoadingState={true}
      />
    )
  }
}