var fs = require('fs');
function get_line(filename, line_no, callback) {
var stream = fs.createReadStream(filename, {
flags: 'r',
encoding: 'utf-8',
fd: null,
mode: 0666,
bufferSize: 64 * 1024
});
var fileData = '';
stream.on('data', function(data){
fileData += data;
// The next lines should be improved
var lines = fileData.split("\n");
if(lines.length >= +line_no){
stream.destroy();
callback(null, lines[+line_no]);
}
});
stream.on('error', function(){
callback('Error', null);
});
stream.on('end', function(){
callback('File end reached without finding line', null);
});
}
get_line('./file.txt', 1, function(err, line){
console.log('The line: ' + line);
})
您应该使用slice方法而不是循环。
var fs = require('fs');
function get_line(filename, line_no, callback) {
var data = fs.readFileSync(filename, 'utf8');
var lines = data.split("\n");
if(+line_no > lines.length){
throw new Error('File end reached without finding line');
}
callback(null, lines[+line_no]);
}
get_line('./file.txt', 9, function(err, line){
console.log('The line: ' + line);
})
for（var l in lines）不是遍历数组的最有效方法，您应该这样做：
for(var i = 0, iMax = lines.length; i < iMax; i++){/* lines[i] */ }
var fs = require('fs');
function get_line(filename, line_no, callback) {
fs.readFile(filename, function (err, data) {
if (err) throw err;
// Data is a buffer that we need to convert to a string
// Improvement: loop over the buffer and stop when the line is reached
var lines = data.toString('utf-8').split("\n");
if(+line_no > lines.length){
return callback('File end reached without finding line', null);
}
callback(null, lines[+line_no]);
});
}
get_line('./file.txt', 9, function(err, line){
console.log('The line: ' + line);
})
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