如何在ionic-4中将多张图片（图像选择器）上传到firebase存储

Question

有人知道如何在Ionic 4中将多个图像（图像选择器）上传到Firebase存储中。下面使用的代码，但是当我单击按钮将图像上传到Firebase存储中时，该图像未加载到Firebase存储中。

<ion-row>
  <ion-col text-center>
    <ion-button (click)="getImages()">Choose Images</ion-button>
  </ion-col>
</ion-row>
<ion-row>

JavaScript：

getImages() {

    this.options = {

        maximumImagesCount: 3,
        width: 200,
        quality: 25,
        outputType: 1
    };


    this.imagePicker.getPictures(this.options).then((results) => {

        for (var i = 0; i < results.length; i++) {

            this.uploadImgToFirebaseStorage(results[i]);

        }
    }, (err) => {
        alert(err);
    });
}


uploadImgToFirebaseStorage(imageData) {

    var base64Str = 'data:image/jpeg;base64,' + imageData;
    var storageRef = firebase.storage().ref();
    var childRef = storageRef.child('firebasestorage.jpg');
    childRef.putString(base64Str, 'data_url').then(function(snapshot) {
            console.log("successfully uploaded...");
        }

    );

}