fs 文件操作
文件操作
require("fs");1.複製文件
創建一個class2.js檔案
在class.js輸入:
fs = require("fs");
function copy(src, target) {
console.log(target);
fs.writeFileSync(target, fs.readFileSync(src));
}
copy("./class1.js","./class2.js");但這樣的寫法容易產生內存溢出，以及同步阻塞
可改成
class.js
fs = require("fs");
function copy(src, target) {
fs.createReadStream(src).pipe(fs.createWriteStream(target));
};
copy("./class1.js","./class2.js");2.同步讀取文件
fs = require("fs");
fileName ="./class1.js";
var text = fs.readFileSync(fileName, "utf8");
console.log(text);3.同步寫入文件
fs = require("fs");
fileName ="./class2.js";
str="abc";
var text = fs.writeFileSync(fileName,str,"utf8");
console.log(text);發現class2.js整個文件變成abc，如果我只想讓abc附加在文件後呢?
改為appendFileSync
fs = require("fs");
fileName ="./class2.js";
str="abc";
var text = fs.appendFileSync(fileName,str,"utf8");
console.log(text);4.判斷路徑是否存在
exists(path, callback)
fs = require("fs");
fileName ="./class2.js";
fs.exists(fileName, function (exists) {
console.log(exists ? "it's there" : "no file!");
});5.移除檔案
先新建一個class3.js
var fs = require('fs');
var filePath = "./class3.js" ;
fs.unlinkSync(filePath);發現class3.js被移除了
6.移除資料夾
先新建一個名為class3的資料夾
var fs = require('fs');
var filePath = "./class3" ;
fs.rmdir(filePath);7.創建資料夾
var fs = require('fs');
fs.mkdir('./IamDir',0777, function (err) {
if (err) throw err;
});但不知道第二個參數是什麼意思，他是指檔案權限的意思，但檔案權限是什麼意思?
下面講一下檔案權限
讀取 Read = R = 4
寫入 Write = W = 2
執行 eXecute = X = 1
Owner = 程式擁有人
Group = 同一群組的其它帳號
Other = 全世界，如訪客
(1) 如果您要開放檔案給任何人 "讀取"、並能 "寫入"，那麼：
Owner (程式擁有人) = 4 + 2 + 0 = 6
Group (同一群組) = 4 + 2 + 0 = 6
Other (訪客) = 4 + 2 + 0 = 6
所以 Owner Group Other = 666
(2) 如果您要開放檔案給任何人執行，自己可以更改檔案，但是不希望其它人更改您的檔案，那麼：
Owner (程式擁有人) = 4 + 2 + 1 = 7
Group (同一群組) = 4 + 0 + 1 = 5
Other (訪客) = 4 + 0 + 1 = 5
所以 Owner Group Other = 7558.readFile是異步的
var fs = require('fs');
fs.readFile('./class1.js','UTF-8' ,function (err, data) {
if (err) throw err;
console.log(data);
});
fs.readFile('./class2.js','UTF-8' ,function (err, data) {
if (err) throw err;
console.log(data);
});
fs.readFile('./class3.js','UTF-8' ,function (err, data) {
if (err) throw err;
console.log(data);
});多嘗試幾次，發現console的讀取順序不固定 9.同步讀取
mkdirSync()，writeFileSync()，readFileSync()10.讀取目錄內檔案
var fs = require('fs');
dir="./as";
fs.readdir(dir, function (err, files) {
if (err) {
console.log(err);
return;
};
console.log(files);
});會返回一個檔案名稱產生的陣列
11.查看檔案詳細資訊
fs.stat(path, callback)
var fs = require('fs');
dir="./as";
fs.readdir(dir, function (err, files) {
if (err) {
return;
};
console.log(files);
files.forEach( function (file) {
fs.stat('./as/' + file, function (err, stats) {
if (err) throw err;
console.log(stats);
});
});
});12.監聽文件
watchfile()，unwatchfile()
var fs = require('fs');
fs.watchFile('./class1.js', function (curr, prev) {
console.log('the current mtime is: ' + curr.mtime);
console.log('the previous mtime was: ' + prev.mtime);
});執行node class後在class1.js寫上東西後按儲存即會在console顯示訊息
13.createReadStream
createReadStream方法往往用於打開大型的文本文件，創建一個讀取操作的數據流。所謂大型文本文件，指的是文本文件的體積很大，讀取操作的緩存裝不下，只能分成幾次發送，每次發送會觸發一個data事件，發送結束會觸發end事件。
var fs = require('fs');
var input = fs.createReadStream('./class1.js');
input.on('data', function(data) {
console.log(data);
});會發現得到的是一個buffer
console.log(data.toString());加上後轉為string
另外
data.toString();
//還可以指定字元集，預設utf-8
data.toString('ascii');
//更可以Base64 Encode
data.toString('base64');
//可以只把部分的資料變成String
data.toString('utf-8',0,10);為什麼要有buffer?
電腦裡有很多檔案其實不是文字檔案來的。實際上，大部分我們開啟的檔案都是二進制檔案，例如圖片檔案，音訊檔案，簡報等，所有檔案裡的資料其實都是以二進制表示的。所以我們就用Buffer物件去表示檔案的內容，和方便我們閱讀檔案資料的每個位元組。fs.utimes
修改檔案的atime與mtime，其他可參考下面文章
讀取出所有資料夾內的資料夾
const fs = require("fs");
let result = [];
const isDirectory = path => (
fs.lstatSync(path).isDirectory()
)
const isBlockList = dirName => {
const blackList = ['__snapshots__', 'test']
return blackList.some(name => name === dirName);
}
const readDeepDir = (path) => {
if(!isDirectory(path)) {
return
}
const dir = fs.readdirSync(path);
if (dir.length > 1) {
dir.forEach(_dir => {
const absolutePath = path + '/' + _dir;
if(isDirectory(absolutePath) && !isBlockList(_dir)) {
result.push(absolutePath);
}
readDeepDir(absolutePath);
});
}
return result;
};
const dir = readDeepDir('../../aip/src/web/console/src/components');
console.log(dir)
不使用第三方模組解析上傳檔案
第三方模組 e.g. formidable, body-parser
index.html
<!DOCTYPE html>
<html>
<input id="fileInput" type="file"></input>
<button onclick="uploadFile()">上傳</button>
<script>
function uploadFile() {
const fileInput = document.querySelector('#fileInput');
const file = fileInput.files[0];
const reader = new FileReader();
reader.readAsArrayBuffer(file);
reader.onload = function () {
const arrayBuffer = reader.result
const bytes = new Uint8Array(arrayBuffer);
console.log(bytes)
fetch('http://localhost:5000', {
method: 'POST', // or 'PUT'
body: JSON.stringify({
file: bytes
}), // data can be `string` or {object}!
headers: new Headers({
'Content-Type': 'application/json'
})
}).then(res => res.json())
.catch(error => console.error('Error:', error))
.then(response => console.log('Success:', response));
}
}
</script>
</html>server.js
const http = require('http');
const setCORS = () => {
const headers = {};
headers["Access-Control-Allow-Origin"] = "*";
headers["Access-Control-Allow-Methods"] = "POST, GET, PUT, DELETE, OPTIONS";
headers["Access-Control-Allow-Credentials"] = false;
headers["Access-Control-Max-Age"] = '86400'; // 24 hours
headers["Access-Control-Allow-Headers"] = "X-Requested-With, X-HTTP-Method-Override, Content-Type, Accept";
return headers
}
const parseBody = (req, callback) => {
let body = '';
req.on('data', chunk => {
body += chunk.toString();
});
req.on('end', () => {
callback(body);
});
}
http.createServer(function (req, res) {
if (req.method === 'OPTIONS') {
const headers = setCORS();
res.writeHead(200, headers);
res.end();
}
if (req.url === '/') {
if (req.method === "POST") {
parseBody(req, (body) => {
console.log(Utf8ArrayToStr(Object.values(JSON.parse(body).file)));
// Utf8ArrayToStr 換成用 Buffer.from 也可以
const headers = setCORS();
res.writeHead(200, headers);
res.end(JSON.stringify({ result: 'ok' }));
})
}
}
}).listen(5000);
function Utf8ArrayToStr(array) {
var out, i, len, c;
var char2, char3;
out = "";
len = array.length;
i = 0;
while (i < len) {
c = array[i++];
switch (c >> 4) {
case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
// 0xxxxxxx
out += String.fromCharCode(c);
break;
case 12: case 13:
// 110x xxxx 10xx xxxx
char2 = array[i++];
out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
break;
case 14:
// 1110 xxxx 10xx xxxx 10xx xxxx
char2 = array[i++];
char3 = array[i++];
out += String.fromCharCode(((c & 0x0F) << 12) |
((char2 & 0x3F) << 6) |
((char3 & 0x3F) << 0));
break;
}
}
return out;
}
console.log('Server running on port 5000.');但之後會發現檔案太大還是會 browser crash，大約 4mb以上，所以還是要用form/data來傳，並用 formidable 解析，如果不用其他模組仍可解析，但要自己parse ------WebKitFormBoundary 內的內容
因為 form/data 可以直接傳入 file input 的 files[0] 類行為 blob，但如果要用 post 必須在 body 傳入 arraybuffer，如果太大會導致 browser crash
上傳 file 轉為 stream
假設檔案長這樣
此時可用
fs.createReadStream(file.path)將其轉為 stream 然後上傳到 minio 或 S3 之類地方。
將檔案從server 傳到 client
1.可用 express 之 res.download('檔案路徑')
或是使用
async function get (req, res) {
const fileName = 'model-sample-1.1_new.json';
const readStream = new stream.PassThrough();
const file = fs.readFileSync(`${__dirname}/${fileName}`);
readStream.end(Buffer.from(file));
res.set('Content-disposition', 'attachment; filename=' + fileName);
readStream.pipe(res);
}在前端部分可以如下下載檔案
window.open(toFullUrl('api/download/template'));前端取得上傳檔案進度
const request = new XMLHttpRequest();
request.open("POST", "http://localhost:3923/file");
request.upload.addEventListener(
"progress",
function(evt) {
if (evt.lengthComputable) {
var percentComplete = evt.loaded / evt.total;
console.log(percentComplete);
}
},false);
request.send(formData);axios 取得上傳進度
axios.post(toFullUrl('api/upload'), formData, {
onUploadProgress: (progressEvent) => {
const percentCompleted = Math.round((progressEvent.loaded * 100) / progressEvent.total)
console.log(percentCompleted)
}
}).then(res => {
...
})Fetch API 目前還無法取得上傳進度
大檔案切片上傳
在前端把檔案切分，分成多的請求上傳，然後在後端合併。
clone 之後進入範例：resumable.js/samples/Node.js
然後把這幾個部分改一下：
前端
var r = new Resumable({
target:'http://localhost:3000/upload',
chunkSize:1*1024*1024,
simultaneousUploads:4,
testChunks:false,
throttleProgressCallbacks:1
});後端
app.js has been tweaked to send resumable a directory where to save the file (top most).
var resumable = require('./resumable-node.js')(__dirname + "/uploads");// Handle uploads through Resumable.js
app.post('/upload', function(req, res){
resumable.post(req, function(status, filename, original_filename, identifier){
if (status === 'done') {
var stream = fs.createWriteStream('./uploads/' + filename);
//stich the chunks
resumable.write(identifier, stream);
stream.on('data', function(data){});
stream.on('end', function(){});
//delete chunks
resumable.clean(identifier);
}
res.send(status, {
// NOTE: Uncomment this funciton to enable cross-domain request.
//'Access-Control-Allow-Origin': '*'
});
});
});產生大檔案
const fs = require('fs');
const GB = 1;
const byteSize = 1000 * 1000 * 1000 * GB;
fs.writeFileSync('./bigfile.txt', Buffer.alloc(byteSize));1024 or 1000
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