How to use JSON data in Node.js?

First you need to parse the JSON file:

let fs = require('fs');
let content = fs.readFileSync('PathToFile').toString();

Then you need to parse it:

let jsonData = JSON.parse(content);

Then iterate over the elements. I recommend the for...of loop

let total = 0;
for(let element of jsonData){
    total += element.low
}

You can also use Array.prototype.map or Array.prototype.reduce but first stick to the basics.

Also please be sure to work on the right types:

your numbers in the JSON are saved as strings. You will have to convert them also:

let total = 0;
for(let element of jsonData){
    total += parseFloat(element.low);
}

please use Object.values like below. Convert JSON to object though using 'JSON.Parse' method

let sum = 0;
Object.values(YOURJSONOBJECT).forEach(element => {

sum += parseFloat(element["low"]);

});

console.log(sum);

and result would be "0.18740099999999998", which is the sum of 'low' property

Just iterate over the object and sum the total

var data =  [{
    "open": "0.06252000",
    "high": "0.06264700",
    "low": "0.06239800",
    "close": "0.06254100",
    "volume": "681.69300000",
    "timestamp": 1521575400000
},
{
    "open": "0.06253500",
    "high": "0.06270000",
    "low": "0.06242800",
    "close": "0.06261900",
    "volume": "371.99900000",
    "timestamp": 1521575700000
},
{
    "open": "0.06261500",
    "high": "0.06280000",
    "low": "0.06257500",
    "close": "0.06266200",
    "volume": "519.11000000",
    "timestamp": 1521576000000
}]
var lowTotal = 0;
data.map(a=>lowTotal+=+a.low)
console.log(lowTotal)

You can do this with a one-liner using reduce()

let sum = words.reduce((a,c)=>a+parseFloat(c.low), 0);

You should fix your code a bit:

let lowTotal = 0;
for(item in words){
    lowTotal += item.low;
}

Or you can do it in a bit different way:

let lowTotal = 0;
words.forEach(word => lowTotal += word.low);

Or the most elegant way:

let lowTotal = words.reduce((a, b) => {
    if(isNaN(a)) { a = a.low; }
    return a + b.low;
}

I am not sure if you are having trouble reading json file but there are bugs in your code

var lowTotal = 0; should be outside for loop.

Parse String JSON object to float

Read item not words

 var lowTotal = 0;
for(item in words){
    lowTotal += parseFloat(item.low);
 }

You can reduce to give an initial value & increment per item in the array

const json = JSON.parse('...');
const lowTotal = json.reduce((val, item) => val += parseFloat(item.low), 0);

Example

const data = `[{
  "open": "0.06252000",
  "high": "0.06264700",
  "low": "0.06239800",
  "close": "0.06254100",
  "volume": "681.69300000",
  "timestamp": 1521575400000
},
{
  "open": "0.06253500",
  "high": "0.06270000",
  "low": "0.06242800",
  "close": "0.06261900",
  "volume": "371.99900000",
  "timestamp": 1521575700000
},
{
  "open": "0.06261500",
  "high": "0.06280000",
  "low": "0.06257500",
  "close": "0.06266200",
  "volume": "519.11000000",
  "timestamp": 1521576000000
}]`;

const json = JSON.parse(data);
const lowTotal = json.reduce((val, item) => val += parseFloat(item.low), 0);
console.log(`Total low=${lowTotal}`);

As some other suggested. But brackets around your tickerdata to create an array.

Another suggestion.

var tickers = require('./JSONFILE.json')

for (const value of Object.values(tickers)) {

  console.log(value.low)

}

since you probably don't want to sum all low values.

For..in is used to iterate over properties of an object. there are many ways to loop throw an array of object, the easiest is to use for. one last thing the lowTotal variable should be declared outside the loop:

var words= [{
    "open": "0.06252000",
    "high": "0.06264700",
    "low": "0.06239800",
    "close": "0.06254100",
    "volume": "681.69300000",
    "timestamp": 1521575400000
},
{
    "open": "0.06253500",
    "high": "0.06270000",
    "low": "0.06242800",
    "close": "0.06261900",
    "volume": "371.99900000",
    "timestamp": 1521575700000
},
{
    "open": "0.06261500",
    "high": "0.06280000",
    "low": "0.06257500",
    "close": "0.06266200",
    "volume": "519.11000000",
    "timestamp": 1521576000000
}];

var lowTotal = 0;
for(var i=0; i<words.length; i++){
  lowTotal += parseFloat(words[i].low);
}

console.log(lowTotal);