node.js readFile的大小

Question

in php i use

 $filename = "a.txt";
 $handle = fopen($filename, "r");
  $heading = fread($handle, 4);
  fclose($handle);
  print $heading;

a.txt content

hello every one

and the output its

hell

now in node.js i use

fs = require('fs');
    fs.readFile('a.txt', 'utf8', function (err,data) {
    if (err) {
    return console.log(err);
    }
    console.log(data);
    });

its output

hello every one

how can i use size length on node.js ?

Answer 1

Here is a basic example:

var fs = require("fs");
var fileName = "a.txt";

fs.open(fileName, "r", function(error, fd) {
  var buffer = new Buffer(4);
  fs.read(fd, buffer, 0, 4, null, function(error, bytesRead, buffer) {
    var data = buffer.toString("ascii", 0, buffer.length);
    console.log(data);
    fs.close(fd);
  });
});

Answer 2

You should be able to use something like this: http://www.w3schools.com/jsref/jsref_substring.asp

with: data.substring(0,4);