如何将 Base64 字符串转换为 javascript 文件对象,就像从文件输入表单一样? [英] How to convert Base64 String to javascript file object like as from file input form?
问题描述
我想将从文件中提取的 Base64String(例如:AAAAA....~")转换为 javascript 文件对象.
I want to convert Base64String extracted from file(ex: "AAAAA....~") to a javascript file object.
javascript文件对象我的意思是这样的代码:
The javascript file object what I mean is like this code:
HTML:
<input type="file" id="selectFile" >
JS:
$('#selectFile').on('change', function(e) {
var file = e.target.files[0];
console.log(file)
}
'file' 变量是一个 javascript 文件对象.所以我想将 base64 字符串转换为这样的 javascript 文件对象.
'file' variable is a javascript file object. So I want to convert a base64 string to the javascript file object like that.
我只想通过解码 base64 字符串(由文件中的其他应用程序编码)来获取文件对象,而无需 html 文件输入表单.
I just want to get file object by decoding base64 string (encoded by other app from a file) without html file input form.
谢谢.
推荐答案
方式 1: 仅适用于 dataURL,不适用于其他类型的 url.
Way 1: only works for dataURL, not for other types of url.
function dataURLtoFile(dataurl, filename) {
var arr = dataurl.split(','),
mime = arr[0].match(/:(.*?);/)[1],
bstr = atob(arr[1]),
n = bstr.length,
u8arr = new Uint8Array(n);
while(n--){
u8arr[n] = bstr.charCodeAt(n);
}
return new File([u8arr], filename, {type:mime});
}
//Usage example:
var file = dataURLtoFile('data:text/plain;base64,aGVsbG8gd29ybGQ=','hello.txt');
console.log(file);
方式 2: 适用于任何类型的 url,(http url、dataURL、blobURL 等...)
Way 2: works for any type of url, (http url, dataURL, blobURL, etc...)
//return a promise that resolves with a File instance
function urltoFile(url, filename, mimeType){
return (fetch(url)
.then(function(res){return res.arrayBuffer();})
.then(function(buf){return new File([buf], filename,{type:mimeType});})
);
}
//Usage example:
urltoFile('data:text/plain;base64,aGVsbG8gd29ybGQ=', 'hello.txt','text/plain')
.then(function(file){ console.log(file);});
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