检查移动设备中的网络连接并处理

Question

我试图通过以下方法调用API之前先在线检查设备

1. If connectivity call api.
2. If no connectivity just show alert.

在这里可以帮忙

getArea() {

this.loading = this.loadingCtrl.create({
  content: "loading..."
});
this.loading.present();
this.userID = "jmzw";
return this.http
    .post(OMWConstants._postsURL + "Areas", 'userID="' + this.userID + '"', {
        headers: this.getPostAPIHeader()
    }
).toPromise().then(data => {
    this.saveArea(data);
    this.loading.dismiss();
    return data;
}).catch(error => {
    this.loading.dismiss();
    this.handleError(error);
});
}