JavaScript Data Not Appending to Array

Question

I have an object of values and I am trying to populate two arrays with the keys and values from the object.

My Object:

obj = {19455746: 7476, 22489710: 473}

Loop attempting to append data:

var sensorNameArray = [];
var sensorDataArray = [];
for(var i in obj) {
  sensorNameArray.push[i];
  sensorDataArray.push[obj[i]];
}

At the moment the two arrays are printing out as empty. My expected outout would be something like:

sensorNameArray = [19455746, 22489710];
sensorDataArray = [7476, 473];

Your syntax is incorrect, it should be push(), not push[] — Lennholm
– Lennholm, Commented Aug 9, 2017 at 10:27
haha thanks, don't know how I didn't spot that. All working now. — Colin747
– Colin747, Commented Aug 9, 2017 at 10:28
@MikaelLennholm if you want to add that comment as an answer I'll accept. — Colin747
– Colin747, Commented Aug 9, 2017 at 10:29

Djaouad · Accepted Answer · 2017-08-09 10:28:56Z

2

push is a function, not an array, it uses parenthesis not brackets :

for(var i in obj) {
    sensorNameArray.push(i);
    sensorDataArray.push(obj[i]);
}

answered Aug 9, 2017 at 10:28

Djaouad

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Comments

Lennholm · Accepted Answer · 2017-08-09 10:33:04Z

0

The syntax push[] doesn't invoke the function, it tries to access a property of the function object. It doesn't throw an error because in Javascript, functions ARE objects and this syntax is technically valid.

So, just fix the syntax to push() in order to actually invoke the function.

answered Aug 9, 2017 at 10:33

Lennholm

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Comments

Rahul Verma · Accepted Answer · 2017-08-09 10:31:18Z

0

You are using square braces [] but array.push() is a function so use circle braces instead

Try the following code

   obj = {19455746: 7476, 22489710: 473};
    var sensorNameArray = [];
    var sensorDataArray = [];
    for(var i in obj) {
      sensorNameArray.push(i);
      sensorDataArray.push(obj[i]);
    }

This is working and tested.

answered Aug 9, 2017 at 10:31

Rahul Verma

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Comments

Jeremy Thille · Accepted Answer · 2017-08-09 10:35:53Z

0

A different syntax (more elegant IMO) :

var sensorNameArray = Object.keys(obj)
var sensorDataArray = Object.values(obj)

or :

var sensorDataArray = sensorNameArray.map( key => obj[key] )

edited Aug 9, 2017 at 10:35

answered Aug 9, 2017 at 10:30

Jeremy Thille

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Comments

ATUL SHARMA · Accepted Answer · 2017-08-09 10:37:24Z

0

Best way to deal with JSON is use lodash or underscore.

_.key() and _.value are functions for your requirement.

Eg.:

obj = {19455746: 7476, 22489710: 473};

sensorNameArray = _.keys(obj);
sensorDataArray = _.values(obj);

If you want to proceed in your way, then you can use parenthesis as push inbuilt function of Javascript for inserting element into array.

Correct is:

for(var i in obj) {
    sensorNameArray.push(i);
    sensorDataArray.push(obj[i]);
}

answered Aug 9, 2017 at 10:37

ATUL SHARMA

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2 Comments

Lennholm Over a year ago

This isn't JSON

ATUL SHARMA Over a year ago

Ya I'm just suggesting other ways, to access objects, so it might be helpful in future. Correction of current code is also specified.

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