Execute Code as Fast as Possible - json

Question

I am using node.js with my WebStorm IDE to parse a large JSON file (~500 megabytes). Here is my code:
fs = require("fs");
fs.readFile('C:/Users/.../Documents/AAPL.json', 'utf8', function (err,data) {
for (i = 0; i < 1000; i++) {
var hex = JSON.parse(data)[i]._source.layers.data["data.data"];
var askPrice = parseInt(hex.substring(215, 239).split(":").reverse().join(""),16);
var bidPrice = parseInt(hex.substring(192, 215).split(":").reverse().join(""),16);
var symbol = hex.substring(156, 179);
var timestamp = hex.substring(132, 155);
var askSize = hex.substring(240, 251);
var bidSize = hex.substring(180, 191);
var price = String((+bidPrice+askPrice)/2);
var realprice = price.slice(0, price.length - 4) + "." + price.slice(price.length - 4);
function hex2a(hexx) {
var hex = hexx.toString();
var str = '';
for (var i = 0; i < hex.length; i += 2)
str += String.fromCharCode(parseInt(hex.substr(i, 2), 16));
return str;
}
if(JSON.parse(data)[i]._source.layers.data["data.len"] == 84 && realprice.length == 8 && +realprice <154 && +realprice >145) {
console.log(i + " " + hex2a(symbol.replace(/:/g, "")) + " sold for " + realprice + " at " + parseInt(timestamp.split(":").reverse().join(""), 16));
}
}
});
The problem I am running into however is that my IDE is parsing this file at an extremely slow speed, roughly 1 iteration a second. I do not think this is because I have a slow computer, for I have a high end rig with a core i7 7700k and a gtx 1070. I tried executing the code in the console with the same result. I tried trimming down the code and again I achieved the same speed:
fs = require("fs");
fs.readFile('C:/Users/Brandt Winkler Prins/Documents/AAPL.json', 'utf8', function (err,data) {
for (i = 0; i < 12000; i++) {
var hex = JSON.parse(data)[i]._source.layers.data["data.data"];
var askPrice = parseInt(hex.substring(215, 239).split(":").reverse().join(""),16);
var bidPrice = parseInt(hex.substring(192, 215).split(":").reverse().join(""),16);
var price = String((+bidPrice+askPrice)/2);
var realprice = price.slice(0, price.length - 4) + "." + price.slice(price.length - 4);
if(+realprice <154 && +realprice >145) {
console.log(realprice);
}
}
});
How should I execute my code to get my data as fast as possible?

Answer 1

You're running JSON.parse(data) every iteration, that might take quite some time for a 500MB json file.
The solution would be to move it out of the loop and reuse the parsed object:
var obj = JSON.parse(data);
for (...