parse array of json with node.js

Question

I'm new to node.js so apologies if this is something very simple.

I have the below node js script:

var http = require("http");
var bodyParser = require("body-parser");

var options =  {
    "method" : "GET",
    "hostname" : "xxx.xxx.xxx.xxx",
    "port" : "18080",
    "path" : "/api/v1/applications/app-20180103124606-0007/stages/0"
};

var req = http.request(options, function (res) {
    var chunks = [];

    res.on("data", function (chunk) {
        chunks.push(chunk);
    });

    res.on("end", function () {
        var body = JSON.parse(Buffer.concat(chunks));
        console.log(body);
    });
});

req.end();

It returns this JSON:

[ { status: 'COMPLETE',
    stageId: 0,
    attemptId: 0,
    numActiveTasks: 0,
    numCompleteTasks: 1,
    numFailedTasks: 0,
    executorRunTime: 2738,
    executorCpuTime: 1207164005,
    submissionTime: '2018-01-03T12:46:10.796GMT',
    firstTaskLaunchedTime: '2018-01-03T12:46:10.810GMT',
    completionTime: '2018-01-03T12:46:14.513GMT',
    inputBytes: 0,
    inputRecords: 99171,
    outputBytes: 0,
    outputRecords: 0,
    shuffleReadBytes: 0,
    shuffleReadRecords: 0,
    shuffleWriteBytes: 1468516,
    shuffleWriteRecords: 3872,
    memoryBytesSpilled: 0,
    diskBytesSpilled: 0,
    name: 'reduceByKey at /scripts/wordcount.py:37',
    details: 'org.apache.spark.rdd.RDD.<init>(RDD.scala:104)\norg.apache.spark.api.python.PairwiseRDD.<init>(PythonRDD.scala:391)\nsun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)\nsun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)\nsun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)\njava.lang.reflect.Constructor.newInstance(Constructor.java:423)\npy4j.reflection.MethodInvoker.invoke(MethodInvoker.java:247)\npy4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:357)\npy4j.Gateway.invoke(Gateway.java:236)\npy4j.commands.ConstructorCommand.invokeConstructor(ConstructorCommand.java:80)\npy4j.commands.ConstructorCommand.execute(ConstructorCommand.java:69)\npy4j.GatewayConnection.run(GatewayConnection.java:214)\njava.lang.Thread.run(Thread.java:748)',
    schedulingPool: 'default',
    accumulatorUpdates: 
     [ [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object],
       [Object] ],
    tasks: { '0': [Object] },
    executorSummary: { '0': [Object] } } ]

I now need to extract launchTime and taskTime. How is this done? I had previousy managed to extract data from JSON but I think I'm having trouble here as it's contained in an array.

It will always be one so went with Jim's anwer. Thanks for the responses. — pac
– pac, Commented Jan 6, 2018 at 16:03

peteb · Accepted Answer · 2018-01-05 13:02:16Z

3

You can use Array.prototype.forEach() to iterate over each member of the response body.

res.on('end', () => {
  let body = JSON.parse(Buffer.concat(chunks))
  body.forEach(item => {
     // Do something with item
     console.log(item)
  })
})

answered Jan 5, 2018 at 13:02

peteb

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Jim Wright · Accepted Answer · 2018-01-05 13:04:47Z

2

If the array length is always 1, then you can access the first array element with body[0].

body[0].executorRunTime
body[0].firstTaskLaunchedTime

Otherwise you could iterate over the result with body.forEach().

answered Jan 5, 2018 at 13:04

Jim Wright

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