Node.js how to read one line of numbers from a file into an array
I have a homework assignment where I have files of numbers to read into an array and then do something with them.
Now, my problem isn't reading the files in. I know how to do that. What i'm unsure on is how to get it to read one line into the array, so that the program can do whatever it is I'm supposed to do, and read in the next line when it's done working with that line of numbers.
The txt files are pretty big, with something like 90 numbers per line and each line ended with a line return.
Any tips on how to make the program read just one line into the array at a time would be greatly appreciated. Thank you.
我认为最简单的方法是使用fs.Readstream如果文件很大。
var fs = require('fs');
var
remaining = "";
lineFeed = "n",
lineNr = 0;
fs.createReadStream('data.txt', { encoding: 'utf-8' })
.on('data', function (chunk) {
// store the actual chunk into the remaining
remaining = remaining.concat(chunk);
// look that we have a linefeed
var lastLineFeed = remaining.lastIndexOf(lineFeed);
// if we don't have any we can continue the reading
if (lastLineFeed === -1) return;
var
current = remaining.substring(0, lastLineFeed),
lines = current.split(lineFeed);
// store from the last linefeed or empty it out
remaining = (lastLineFeed > remaining.length)
? remaining.substring(lastLineFeed + 1, remaining.length)
: "";
for (var i = 0, length = lines.length; i < length; i++) {
// process the actual line
_processLine(lines[i], lineNr++);
}
})
.on('end', function (close) {
// TODO I'm not sure this is needed, it depends on your data
// process the reamining data if needed
if (remaining.length > 0) _processLine(remaining, lineNr);
});
function _processLine(line, lineNumber) {
// UPDATE2 with parseFloat
var numbers = line.split(" ").map(function (item) { return parseFloat(item); });
console.log(numbers, lineNumber);
}
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