Node.js內置的fs模塊就是文件系統(tǒng)模塊，負責讀寫文件版仔，提供了異步和同步的方法朗徊。
異步讀文件
'use strict';
var fs = require('fs');
fs.readFile('sample.txt', 'utf-8', function (err, data) {
if (err) {
console.log(err);
} else {
console.log(data);
}
});
sample.txt文件必須在當前目錄下，且文件編碼為utf-8
正常讀取時株旷，err參數(shù)為null，data參數(shù)為讀取到的String
取發(fā)生錯誤時疤估，err參數(shù)代表一個錯誤對象灾常，data為undefined。
讀取圖片文件
'use strict';
var fs = require('fs');
fs.readFile('sample.png', function (err, data) {
if (err) {
console.log(err);
} else {
console.log(data);
console.log(data.length + ' bytes');
}
});
回調函數(shù)的data參數(shù)將返回一個Buffer對象
Buffer對象轉換成String：
// Buffer -> String
var text = data.toString('utf-8');
console.log(text);
String轉換成Buffer：
// String -> Buffer
var buf = new Buffer(text, 'utf-8');
console.log(buf);
同步讀文件
'use strict';
var fs = require('fs');
var data = fs.readFileSync('sample.txt', 'utf-8');
console.log(data);
try {
var data = fs.readFileSync('sample.txt', 'utf-8');
console.log(data);
} catch (err) {
// 出錯了
}
寫文件
'use strict';
var fs = require('fs');
var data = 'Hello, Node.js';
fs.writeFile('output.txt', data, function (err) {
if (err) {
console.log(err);
} else {
console.log('ok.');
}
});
如果傳入的數(shù)據(jù)是String铃拇，默認按UTF-8編碼寫入文本文件钞瀑，如果傳入的參數(shù)是Buffer，則寫入的是二進制文件慷荔。
同步寫文件
'use strict';
var fs = require('fs');
var data = 'Hello, Node.js';
fs.writeFileSync('output.txt', data);
stat
'use strict';
var fs = require('fs');
fs.stat('sample.txt', function (err, stat) {
if (err) {
console.log(err);
} else {
// 是否是文件:
console.log('isFile: ' + stat.isFile());
// 是否是目錄:
console.log('isDirectory: ' + stat.isDirectory());
if (stat.isFile()) {
// 文件大小:
console.log('size: ' + stat.size);
// 創(chuàng)建時間, Date對象:
console.log('birth time: ' + stat.birthtime);
// 修改時間, Date對象:
console.log('modified time: ' + stat.mtime);
}
}
});
https://github.com/michaelliao/learn-javascript/tree/master/samples/node/fs
read_image_file_async.js
'use strict'
const fs=require('fs');
console.log('>>>> BEGIN >>>>');
fs.readFile(__dirname+'/'+'sample.png',function(err,data){
//'sample.png' => d:\\workspace\\js\\sample.png
//__dirname+'/'+'sample.png' => d:\\workspace\\js\\test\\sample.png
if(err){
console.log(err);
}else{
console.log(data);
console.log(data.length+' bytes');
}
});
console.log('>>> END >>>');
>>>> BEGIN >>>>
>>> END >>>
<Buffer 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 00 00 01 2c 00 00 01 2c 08 06 00 00 00 79 7d 8e 75 00 00 20 00 49 44 41 54 78 9c ec bd bd ba 2d 49 92 ... >
73770 bytes
read_image_file_sync.js
'use strict';
// read from 'sample.png'
const fs = require('fs');
console.log('>>> BEGIN >>>')
var data = fs.readFileSync(__dirname+'/'+'sample.png');
console.log(data);
console.log(data.length + ' bytes');
console.log('>>> END >>>')
>>>> BEGIN >>>>
<Buffer 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 00 00 01 2c 00 00 01 2c 08 06 00 00 00 79 7d 8e 75 00 00 20 00 49 44 41 54 78 9c ec bd bd ba 2d 49 92 ... >
73770 bytes
>>>> END >>>>
read_text_file_async.js
'use strict';
// read text from 'sample.txt'
const fs = require('fs');
console.log('>>> BEGIN >>>')
fs.readFile(__dirname+'/'+'sample.txt', 'utf-8', function (err, data) {
if (err) {
console.log(err);
} else {
console.log(data);
}
});
console.log('>>> END >>>')
>>>> BEGIN >>>>
>>>> END >>>>
Nodejs教程：File I/O is provided by simple wrappers around standard POSIX functions. To use this module do require('fs'). All the methods have asynchronous and synchronous forms.
read_text_file_sync.js
'use strict';
// read text from 'sample.txt'
const fs = require('fs');
console.log('>>> BEGIN >>>')
var data = fs.readFileSync('sample.txt', 'utf-8');
console.log(data);
console.log('>>> END >>>')
use_buffer.js
'use strict';
// read binary data from 'sample.txt'
const fs = require('fs');
var data = fs.readFileSync('sample.txt')
console.log(data);
console.log(data.length + ' bytes');
console.log('First three bytes: ' + data[0] + ', ' + data[1] + ', ' + data[2]);
// Buffer -> String
var text = data.toString('utf-8');
console.log(text);
// String -> Buffer
var buf = new Buffer(text, 'utf-8');
console.log(buf);
<Buffer 4e 6f 64 65 6a 73 e6 95 99 e7 a8 8b ef bc 9a 46 69 6c 65 20 49 2f 4f 20 69 73 20 70 72 6f 76 69 64 65 64 20 62 79 20 73 69 6d 70 6c 65 20 77 72 61 70 ... >
181 bytes
First three bytes: 78,111,100
Nodejs教程：File I/O is provided by simple wrappers around standard POSIX functions. To use this module do require('fs'). All the methods have asynchronous and synchronous forms.
<Buffer 4e 6f 64 65 6a 73 e6 95 99 e7 a8 8b ef bc 9a 46 69 6c 65 20 49 2f 4f 20 69 73 20 70 72 6f 76 69 64 65 64 20 62 79 20 73 69 6d 70 6c 65 20 77 72 61 70 ... >
use_stat.js
'use strict';
const fs = require('fs');
fs.stat('sample.txt', function (err, stat) {
if (err) {
console.log(err);
} else {
console.log('isFile: ' + stat.isFile());
console.log('isDirectory: ' + stat.isDirectory());
if (stat.isFile()) {
console.log('size: ' + stat.size);
console.log('birth time: ' + stat.birthtime);
console.log('modified time: ' + stat.mtime);
}
}
});
isFile: true
isDirectory: false
size: 181
birth time： Wed Jul 05 2017 14:05:20 GMT+0800 (中國標準時間)
modified time: Wed Jul 05 2017 14:05:20 GMT+0800 (中國標準時間)
write_text_file_async.js
'use strict';
// write text to 'output.txt'
const fs = require('fs');
console.log('>>> BEGIN >>>')
var data = 'Hello, Node.js';
fs.writeFile('output.txt', data, function (err) {
if (err) {
console.log(err);
} else {
console.log('ok.');
}
});
console.log('>>> END >>>')
write_text_file_sync.js
'use strict';
// write text to 'output.txt'
const fs = require('fs');
console.log('>>> BEGIN >>>')
var data = 'Hello, Node.js';
fs.writeFileSync('output.txt', data);
console.log('>>> END >>>')
