如果它是一个小文件,你可能会逃脱这样的事情:
// specifying the encoding means you don't have to do `.toString()`
var arrayOfThings = fs.readFileSync("./file", "utf8").trim().split(/[\r\n]+/g).map(function(line) {
// this try/catch will make it so we just return null
// for any lines that don't parse successfully, instead
// of throwing an error.
try {
return JSON.parse(line);
} catch (e) {
return null;
}
// this .filter() removes anything that didn't parse correctly
}).filter(function(object) {
return !!object;
});
如果它更大,您可能需要考虑使用 npm 上的许多模块中的任何一个来逐行读取它,以从流中使用行。
想看看如何使用流来做到这一点?让我们看看我们如何使用流来做到这一点。这不是一个实际的例子,但无论如何它很有趣!
var stream = require("stream"),
fs = require("fs");
var LineReader = function LineReader(options) {
options = options || {};
options.objectMode = true;
stream.Transform.call(this, options);
this._buffer = "";
};
LineReader.prototype = Object.create(stream.Transform.prototype, {constructor: {value: LineReader}});
LineReader.prototype._transform = function _transform(input, encoding, done) {
if (Buffer.isBuffer(input)) {
input = input.toString("utf8");
}
this._buffer += input;
var lines = this._buffer.split(/[\r\n]+/);
this._buffer = lines.pop();
for (var i=0;i<lines.length;++i) {
this.push(lines[i]);
}
return done();
};
LineReader.prototype._flush = function _flush(done) {
if (this._buffer.length) {
this.push(this._buffer);
}
return done();
};
var JSONParser = function JSONParser(options) {
options = options || {};
options.objectMode = true;
stream.Transform.call(this, options);
};
JSONParser.prototype = Object.create(stream.Transform.prototype, {constructor: {value: JSONParser}});
JSONParser.prototype._transform = function _transform(input, encoding, done) {
try {
input = JSON.parse(input);
} catch (e) {
return done(e);
}
this.push(input);
return done();
};
var Collector = function Collector(options) {
options = options || {};
options.objectMode = true;
stream.Transform.call(this, options);
this._entries = [];
};
Collector.prototype = Object.create(stream.Transform.prototype, {constructor: {value: Collector}});
Collector.prototype._transform = function _transform(input, encoding, done) {
this._entries.push(input);
return done();
};
Collector.prototype._flush = function _flush(done) {
this.push(this._entries);
return done();
};
fs.createReadStream("./file").pipe(new LineReader()).pipe(new JSONParser()).pipe(new Collector()).on("readable", function() {
var results = this.read();
console.log(results);
});