如何用javascript FileReader检测文件扩展名 [英] How to detect file extension with javascript FileReader

问题描述

我正在使用javascript的FileReader和我的自定义函数来读取JPG-JPEG图像，
我的问题是如何通过下面的代码检测文件扩展名，如果文件是不是JPG-JPEG：

I'm using javascript's FileReader and my customized function for reading an JPG-JPEG image, My problem is that how it's possible to detect the file extension through my code below and give error to user if the file is not JPG-JPEG:

function readURL(input) {
  if (input.files && input.files[0]) {
    var reader = new FileReader();

    reader.onload = function (e) {
      alert('image has read completely!');
    }

    reader.readAsDataURL(input.files[0]);
  }
}

推荐答案

你可以试试这个，
我改变你的代码如下：

You can try this, I changed your code as follows:

var fileTypes = ['jpg', 'jpeg', 'png', 'what', 'ever', 'you', 'want'];  //acceptable file types

function readURL(input) {
    if (input.files && input.files[0]) {
        var extension = input.files[0].name.split('.').pop().toLowerCase(),  //file extension from input file
            isSuccess = fileTypes.indexOf(extension) > -1;  //is extension in acceptable types

        if (isSuccess) { //yes
            var reader = new FileReader();
            reader.onload = function (e) {
                alert('image has read completely!');
            }

            reader.readAsDataURL(input.files[0]);
        }
        else { //no
            //warning
        }
    }
}

这篇关于如何用javascript FileReader检测文件扩展名的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！