[英]Read JSON from from HTML file input
If I have an input:如果我有输入:
<input type="file" id="upload" onchange="getFile(this)">
And my user will upload a JSON file (as plaintext, so I will have to use JSON.parse()
), how can I take this file and actually get the data via getFile()
我的用户将上传一个 JSON 文件(作为纯文本,所以我将不得不使用JSON.parse()
),我怎样才能获取这个文件并通过getFile()
实际获取数据
In getFile(element)
, I've tried using element.files[0]
but that doesn't seem to contain the actual data.在getFile(element)
中,我尝试使用element.files[0]
,但这似乎不包含实际数据。 I've also looked here , here , and here , but none of these solve my problem.我也看过这里、 这里和这里,但这些都不能解决我的问题。 This resource on MDN seems promising, but I don't really get it. MDN 上的这个资源看起来很有希望,但我真的不明白。
I would like a solution involving either URL.createObjectURL()
or FileReader()
.我想要一个涉及URL.createObjectURL()
或FileReader()
的解决方案。
Also, before anyone posts this in the comments, I do understand that these solutions do not work on all browsers, and I would like to do this from the frontend.此外,在任何人在评论中发布此内容之前,我确实了解这些解决方案不适用于所有浏览器,我想从前端执行此操作。
You could take advantage of the Response constructor and call .json()
on any blob/file.您可以利用Response构造函数并在任何 blob/文件上调用.json()
。
function getFile (elm) {
new Response(elm.files[0]).json().then(json => {
console.log(json)
}, err => {
// not json
})
}
Alternative method using the new read methods on blob.prototype[...]使用 blob.prototype[...] 上的新读取方法的替代方法
new Blob(['1']).text().then(JSON.parse).then(console.log)
I guess for larger files response.json might be faster/better since it can parse the content in background and not block the main UI unlike JSON.parse我猜对于较大的文件响应。json 可能更快/更好,因为它可以解析后台内容并且不会像 JSON.parse 那样阻塞主 UI
I think you need this api:我想你需要这个 api:
FileReader Api From MDN 文件阅读器 Api 来自 MDN
View In Stackblitz 在 Stackblitz 中查看
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Read Text</title>
<style>
div {
margin-top: 30px;
border: solid 1px black;
padding: 5px;
}
</style>
<script>
function processFiles(files) {
var file = files[0];
var message = document.getElementById("message");
message.innerHTML = "File Name:" + file.name + "<br>";
message.innerHTML += "File Size:" + file.size + "<br>";
message.innerHTML += "File Type:" + file.type + "<br>";
var reader = new FileReader();
reader.onload = function (e) {
var output = document.getElementById("fileOutput");
// parse string to json
output.textContent = JSON.parse(e.target.result);
};
reader.readAsText(file);
}
</script>
</head>
<body>
<input id="fileInput" type="file" size="50" onchange="processFiles(this.files)">
<div id="message"></div>
<div id="fileOutput"></div>
</body>
</html>
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