JSON数组到Node.js可读对象流

Question

I have an event that fires every time a packet is received from a bluetooth device. The packet comes in as a JSON array and always contains 10 objects similar to the ones below.

var s1_data = [{"record":0,"sensor":1,"timestamp":26566,"date":{"day":7,"hour":10,"minute":45,"month":5,"second":38,"year":18}},
{"record":1,"sensor":1,"timestamp":26567,"date":{"day":7,"hour":10,"minute":45,"month":5,"second":38,"year":18}},
{"record":2,"sensor":1,"timestamp":26568,"date":{"day":7,"hour":10,"minute":45,"month":5,"second":38,"year":18}},
{"record":3,"sensor":1,"timestamp":26569,"date":{"day":7,"hour":10,"minute":45,"month":5,"second":38,"year":18}},
{"record":4,"sensor":1,"timestamp":26570,"date":{"day":7,"hour":10,"minute":45,"month":5,"second":38,"year":18}},
{"record":5,"sensor":1,"timestamp":26571,"date":{"day":7,"hour":10,"minute":45,"month":5,"second":38,"year":18}},
{"record":6,"sensor":1,"timestamp":26572,"date":{"day":7,"hour":10,"minute":45,"month":5,"second":38,"year":18}},
{"record":7,"sensor":1,"timestamp":26573,"date":{"day":7,"hour":10,"minute":45,"month":5,"second":38,"year":18}},
{"record":8,"sensor":1,"timestamp":26574,"date":{"day":7,"hour":10,"minute":45,"month":5,"second":38,"year":18}},
{"record":9,"sensor":1,"timestamp":26575,"date":{"day":7,"hour":10,"minute":45,"month":5,"second":38,"year":18}}]

I need to push each individual object into a node.js stream that is being consumed by another stream.

Can anyone give an example on how I can push these to a Readable object stream on an ongoing basis (or do I need to use a PassThrough stream)? I can't seem to get my head around how to do this!

Edited to add sample code below. chunk.toString() fails as chunk is undefined

var Readable = require('stream').Readable;
var util = require('util');
var through2 = require('through2');

var s1 = require('./sensor1.js');
var s2 = require('./sensor2.js');

var minLength = s1.length;
//console.log(s1);
var s1stream = new Readable({ objectMode: true });
var s2stream = new Readable({ objectMode: true });


s1stream._read = function () {
    this.push();
};

s2stream._read = function () {
    this.push();
};

if (s2.length < minLength){
  minLength = s2.length;
}

var n1 = 0;
setInterval(function() {
    if (n1++ < minLength) {
        console.log(s1[n1].record);
        s1stream.push(s1[n1]);
    } else if (n1++ === minLength) {
        s1stream.push(null);
    }
}, 1000);

var n2 = 0;
setInterval(function() {
    if (n2++ < minLength) {
        s2stream.push(s2[n2]);
    } else if (n2++ === minLength) {
        s2stream.push(null);
    }
}, 1000);


s1stream.pipe(through2.obj(function (chunk, enc, callback) {
    this.push(chunk.toString())
    callback()
  })).pipe(process.stdout);

Edit below shows working code. Looks like it was to do with the way I was creating the read functions

var Readable = require('stream').Readable;
var util = require('util');
var through2 = require('through2');
var Transform = require('stream').Transform;

var s1 = require('./sensor1.js');
var s2 = require('./sensor2.js');

var minLength = s1.length;
//console.log(s1);

var s1stream = new Readable({
   objectMode: true,
   read() {}
 })

 const s2stream = new Readable({
    objectMode: true,
    read() {}
  })

if (s2.length < minLength){
  minLength = s2.length;
}

var n1 = 0;
setInterval(function() {
    if (n1 < minLength) {
        s1stream.push(s1[n1]);
        n1++;
    } else if (n1 == minLength) {
        s1stream.push(null);
    }
}, 1000);

var n2 = 0;
setInterval(function() {
    if (n2++ < minLength) {
        s2stream.push(s2[n2]);
    } else if (n2++ === minLength) {
        s2stream.push(null);
    }
}, 1000);

var jsonStream = through2.obj(function(file, encoding, cb) {
    this.push(file.record.toString())
    cb()
})

s1stream.pipe(jsonStream).pipe(process.stdout);

Answer 1

You will need to implement a Readable stream that "wraps" your bluetooth source. When the packet received event is fired you'll loop through your array of objects and call your Readable stream's push method, passing in each object. A somewhat similar example of this can be seen here

Note that since you'll be sending actual JSON objects you'll want to enable the objectMode option when you write your implementation as described here