上传图片转base64,报错

Question

报错：ERROR TypeError: Failed to execute 'readAsDataURL' on 'FileReader': parameter 1 is not of type 'Blob'.
这是用ionic写的

\\xx.html
<input type="file" (change)="selectImage(this.files)" accept="image/jpeg,image/png,image/jpg">

\\xx.ts
selectImage(file){
      var reader = new FileReader();
      reader.onload = function(file){
        // console.log(evt.currentTarget)
      }
      reader.readAsDataURL(file);
      console.log(reader.readAsDataURL(file));  
  }

Answer 1

selectImage(event){
      let reader = new FileReader();
      let file = event.target.files[0];
      reader.readAsDataURL(file);
      reader.onload = function(){
        console.log(reader.result)
      }
    }

Answer 2

this.files是个类数组吧，取第一个reader.readAsDataURL(file[0]);

Answer 3

我想问下我怎么把blob转成base64呀。我获取的字符串为：url("blob:http://localhost:8080/cc116c31-f8f1-47b1-a87b-96d948253495")。请大神赐教