Node.js--fs 文件操作
<div><div><strong>process 模块</strong> 在使用的时候无需通过 require() 函数来加载该模块，可以直接使用。</div>
<div><strong>fs 模块</strong>，在使用的时候，必须通过 require() 函数来加载该模块，方可使用。</div>
<div>原因：process 模块是全局的模块，而 fs 模块不是全局模块。全局模块可以直接使用，而非全局模块需要通过 require('') 加载该模块。</div>
<div> </div>
<div>
<div>
<h2>一、实现文件写入操作</h2>
<div class="cnblogs_code">
<pre><span style="color: rgba(0, 128, 128, 1)"> 1</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">1.加载文件操作模块，fs 模块</span>
<span style="color: rgba(0, 128, 128, 1)"> 2</span> <span style="color: rgba(0, 0, 255, 1)">var</span> fs = require('fs'<span style="color: rgba(0, 0, 0, 1)">);
</span><span style="color: rgba(0, 128, 128, 1)"> 3</span>
<span style="color: rgba(0, 128, 128, 1)"> 4</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">2.实现文件写入操作</span>
<span style="color: rgba(0, 128, 128, 1)"> 5</span> <span style="color: rgba(0, 0, 255, 1)">var</span> msg = "hello world,你好世界"<span style="color: rgba(0, 0, 0, 1)">;
</span><span style="color: rgba(0, 128, 128, 1)"> 6</span>
<span style="color: rgba(0, 128, 128, 1)"> 7</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">调用 fs.writeFile() 进行文件写入 </span>
<span style="color: rgba(0, 128, 128, 1)"> 8</span> <span style="color: rgba(0, 128, 0, 1)">// </span><span style="color: rgba(0, 128, 0, 1)">fs.writeFile() 是异步方法</span>
<span style="color: rgba(0, 128, 128, 1)"> 9</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> fs.writeFile('写入文件的路径','要写入的数据','文档编码格式','回调函数')</span>
<span style="color: rgba(0, 128, 128, 1)">10</span> fs.writeFile('hello.txt', msg, 'utf8', (err) =><span style="color: rgba(0, 0, 0, 1)"> {
</span><span style="color: rgba(0, 128, 128, 1)">11</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">如果 err===null,表示文件写入</span>
<span style="color: rgba(0, 128, 128, 1)">12</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">只要 err 里面不是null，就表示写入文件失败了！</span>
<span style="color: rgba(0, 128, 128, 1)">13</span> <span style="color: rgba(0, 0, 255, 1)">if</span><span style="color: rgba(0, 0, 0, 1)"> (err) {
</span><span style="color: rgba(0, 128, 128, 1)">14</span> console.log('写入文件出错拉！具体错误：' +<span style="color: rgba(0, 0, 0, 1)"> err)
</span><span style="color: rgba(0, 128, 128, 1)">15</span> } <span style="color: rgba(0, 0, 255, 1)">else</span><span style="color: rgba(0, 0, 0, 1)"> {
</span><span style="color: rgba(0, 128, 128, 1)">16</span> console.log('ok'<span style="color: rgba(0, 0, 0, 1)">);
</span><span style="color: rgba(0, 128, 128, 1)">17</span> <span style="color: rgba(0, 0, 0, 1)"> }
</span><span style="color: rgba(0, 128, 128, 1)">18</span> });</pre>
</div>
<h2>二、实现文件读取操作</h2>
<div>
<div class="cnblogs_code">
<pre><span style="color: rgba(0, 128, 128, 1)"> 1</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">1.加载文件操作模块，fs 模块</span>
<span style="color: rgba(0, 128, 128, 1)"> 2</span> <span style="color: rgba(0, 0, 255, 1)">var</span> fs = require('fs'<span style="color: rgba(0, 0, 0, 1)">);
</span><span style="color: rgba(0, 128, 128, 1)"> 3</span>
<span style="color: rgba(0, 128, 128, 1)"> 4</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">2.调用 fs.readFile() 方法来读取文件</span>
<span style="color: rgba(0, 128, 128, 1)"> 5</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> fs.readFile('读取文件的路径','文件编码格式','回调函数')</span>
<span style="color: rgba(0, 128, 128, 1)"> 6</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">在读取文件的时候，如果传递了编码格式，那么回调函数中的 data默认就会转换为 字符串，否则data 参数的数据是一个 Buffer 对象，里面保存的就是一个一个的字节(理解为字节数组)</span>
<span style="color: rgba(0, 128, 128, 1)"> 7</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">把 Buffer 对象转换为字符串，调用 toString() 方法</span>
<span style="color: rgba(0, 128, 128, 1)"> 8</span>
<span style="color: rgba(0, 128, 128, 1)"> 9</span> fs.readFile('./hello.txt', 'utf8', (err, data) =><span style="color: rgba(0, 0, 0, 1)"> {
</span><span style="color: rgba(0, 128, 128, 1)">10</span> <span style="color: rgba(0, 0, 255, 1)">if</span><span style="color: rgba(0, 0, 0, 1)"> (err) {
</span><span style="color: rgba(0, 128, 128, 1)">11</span> <span style="color: rgba(0, 0, 255, 1)">throw</span><span style="color: rgba(0, 0, 0, 1)"> err;
</span><span style="color: rgba(0, 128, 128, 1)">12</span> } <span style="color: rgba(0, 0, 255, 1)">else</span><span style="color: rgba(0, 0, 0, 1)"> {
</span><span style="color: rgba(0, 128, 128, 1)">13</span> <span style="color: rgba(0, 0, 0, 1)"> console.log(data);
</span><span style="color: rgba(0, 128, 128, 1)">14</span> <span style="color: rgba(0, 0, 0, 1)"> }
</span><span style="color: rgba(0, 128, 128, 1)">15</span> });</pre>
</div>
<p> </p>
</div>
<div>
<div><strong>1.读取文件中的路径问题</strong></div>
<br>
<div> ./ 相对路径，相对的执行 node 命令的路径，而不是相对于正在执行的这个 js 文件来查找 hello.txt</div>
<br>
<div>解决在文件读取中 ./ 相对路径的问题</div>
<div><strong>解决方法</strong>：使用 __dirname、__filename</div>
<br>
<div>__dirname:表示，当前正在执行的 js 文件所在的目录</div>
<div>___filename:表示，当前正在执行的 js 文件的完整路径</div>
</div>
<div> </div>
<div>
<div>// console.log(__dirname); C:\Users\zhuyujie\Desktop\nodejs\1.fs</div>
<div>// console.log(__filename); C:\Users\zhuyujie\Desktop\nodejs\1.fs\2.fs_readFile.js</div>
</div>
<div><br>
<div><span style="color: rgba(255, 0, 0, 1)">注：</span>__dirname、___filename并不是全局的</div>
<div> </div>
<div>应该将上面代码的路径修改成：</div>
<div>
<div class="cnblogs_code">
<pre><span style="color: rgba(0, 128, 128, 1)"> 1</span> <span style="color: rgba(0, 0, 255, 1)">var</span> fs = require('fs'<span style="color: rgba(0, 0, 0, 1)">);
</span><span style="color: rgba(0, 128, 128, 1)"> 2</span>
<span style="color: rgba(0, 128, 128, 1)"> 3</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> var filename= __dirname+'\\'+'hello.txt'(不推荐使用)</span>
<span style="color: rgba(0, 128, 128, 1)"> 4</span>
<span style="color: rgba(0, 128, 128, 1)"> 5</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">推荐使用通过 path 模块进行路径拼接</span>
<span style="color: rgba(0, 128, 128, 1)"> 6</span> <span style="color: rgba(0, 0, 255, 1)">var</span> path = require('path'<span style="color: rgba(0, 0, 0, 1)">);
</span><span style="color: rgba(0, 128, 128, 1)"> 7</span>
<span style="color: rgba(0, 128, 128, 1)"> 8</span> <span style="color: rgba(0, 0, 255, 1)">var</span> filename = path.join(__dirname, 'hello.txt'<span style="color: rgba(0, 0, 0, 1)">)
</span><span style="color: rgba(0, 128, 128, 1)"> 9</span>
<span style="color: rgba(0, 128, 128, 1)">10</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> console.log(filename);</span>
<span style="color: rgba(0, 128, 128, 1)">11</span>
<span style="color: rgba(0, 128, 128, 1)">12</span> fs.readFile(filename, 'utf8', (err, data) =><span style="color: rgba(0, 0, 0, 1)"> {
</span><span style="color: rgba(0, 128, 128, 1)">13</span> <span style="color: rgba(0, 0, 255, 1)">if</span><span style="color: rgba(0, 0, 0, 1)"> (err) {
</span><span style="color: rgba(0, 128, 128, 1)">14</span> <span style="color: rgba(0, 0, 255, 1)">throw</span><span style="color: rgba(0, 0, 0, 1)"> err;
</span><span style="color: rgba(0, 128, 128, 1)">15</span> <span style="color: rgba(0, 0, 0, 1)"> }
</span><span style="color: rgba(0, 128, 128, 1)">16</span> <span style="color: rgba(0, 0, 0, 1)"> console.log(data);
</span><span style="color: rgba(0, 128, 128, 1)">17</span>
<span style="color: rgba(0, 128, 128, 1)">18</span> });</pre>
</div>
<h2> 三、创建文件夹</h2>
<div class="cnblogs_code">
<pre><span style="color: rgba(0, 128, 128, 1)">1</span> <span style="color: rgba(0, 0, 255, 1)">var</span> fs=require('fs'<span style="color: rgba(0, 0, 0, 1)">);
</span><span style="color: rgba(0, 128, 128, 1)">2</span>
<span style="color: rgba(0, 128, 128, 1)">3</span> fs.mkdir('test-mkdir',(err)=><span style="color: rgba(0, 0, 0, 1)">{
</span><span style="color: rgba(0, 128, 128, 1)">4</span> <span style="color: rgba(0, 0, 255, 1)">if</span><span style="color: rgba(0, 0, 0, 1)"> (err) {
</span><span style="color: rgba(0, 128, 128, 1)">5</span> console.log('创建目录出错了，详情'+<span style="color: rgba(0, 0, 0, 1)">err);
</span><span style="color: rgba(0, 128, 128, 1)">6</span> } <span style="color: rgba(0, 0, 255, 1)">else</span><span style="color: rgba(0, 0, 0, 1)"> {
</span><span style="color: rgba(0, 128, 128, 1)">7</span> console.log('创建目录成功'<span style="color: rgba(0, 0, 0, 1)">);
</span><span style="color: rgba(0, 128, 128, 1)">8</span> <span style="color: rgba(0, 0, 0, 1)">}
</span><span style="color: rgba(0, 128, 128, 1)">9</span> });</pre>
</div>
<p> </p>
</div>
<div> </div>
<div> </div>
</div>
</div>
</div>
</div><br><br>
来源：https://www.cnblogs.com/zhuyujie/p/11600943.html
頁:
[1]