Random number generator does not produce an expected answer Node JS - node.js

Question

In a Node JS script, a formula is being used to generate a random number between two values. Here is the function randomIntInc:
function randomIntInc(low, high) {
return Math.floor(Math.random() * (high - low + 1) + low);
}
The function is called with two values as low and high:
let randomNumber = randomIntInc(requestedStart, requestedEnd);
console.log(requestedStart) before executing the above line produces 542 (expected)
console.log(requestedEnd) before executing the above line produces 592 (expected)
Now, running the above line and logging the output produces any value, generally within 6 and 50.
What is happening? Logging before executing the random number shows the correct ranges, but the outputted number just does not fall within the given range.
Here's the full code (related code at 113) (please ignore bad practice code that's unrelated / memes or easter eggs):
// Copyright (C) 2018, Julian Lachniet, Jacob Wysko
// Dependencies
var Discord = require('discord.io'),
logger = require('winston'),
auth = require('../auth.json'),
rn = require('random-number'),
http = require('http'),
request = require('request');
// Authorize connection
var bot = new Discord.Client({
token: auth.token,
autorun: true
});
// GOOGLE SHEETS API
const fs = require('fs');
const readline = require('readline');
const {google} = require('googleapis');
const SCOPES = ['https://www.googleapis.com/auth/spreadsheets.readonly'];
const TOKEN_PATH = 'credentials.json';
// If bot disconnects, try to reconnect
bot.on('disconnect', function(msg, code) {
if (code === 0) return console.error(msg);
bot.connect();
});
// Returns the current timestamp
function timeStamp() {
return "[" + new Date().toString().split(" G")[0] + "]";
}
// Returns a random integer
function randomIntInc(low, high) {
return Math.floor(Math.random() * (high - low + 1) + low);
}
// When a message is recieved
bot.on('message', function(user, userID, channelID, message, evt) {
let valid = false;
// Log what the user sent (verifies it wasn't sent by the bot)
if (user !== 'teacher-quotes-bot') {
console.log(timeStamp() + " " + user + ": " + message);
}
// Sends a message with text "message", logs it
function sendMessage(message) {
bot.sendMessage({
to: channelID,
message: message
});
console.log(timeStamp() + " Bot: " + message);
valid = true;
}
// Sends a message based on a list of commands
function infoMessage(commands, response) {
if (commands.includes(input)) {
sendMessage(response);
}
validCommands.push(commands);
}
// If the message began with a '!' (e.g., !cmd)
if (message.substring(0, 1) === '!') {
var args = message.substring(1).split(' ');
var input = args[0];
var validCommands = [];
// Commands
infoMessage(['accuracy', 'disclaimer', 'terms'], '<#440534402171404289>');
infoMessage(['android', 'app'], 'https://play.google.com/store/apps/details?id=com.jacobwysko.teacherquotes');
infoMessage(['format', 'formats', 'formatting'], '"Quote text." - Teacher, MM/DD/YYYY');
infoMessage(['code', 'git', 'github', 'roadmap', 'trello', 'source', 'sourcecode'], 'https://github.com/wyskoj/TeacherQuotesVersion3\nhttps://github.com/jlachniet/TeacherQuotesBot');
infoMessage(['faq', 'help', '?'], "You've been <#440504422028804107>ed.");
infoMessage(['ping', 'pong'], 'Pong!');
infoMessage(['rule', 'rules'], "You've been <#440500062011916298>ed");
infoMessage(['apple', 'ios', 'web', 'website'], 'http://jacobwysko.com/teacherquotes');
infoMessage(['cmd', 'cmds', 'command', 'commands'], 'Valid Commands:\n - accuracy\n - app\n - format\n - github\n - help\n - ping\n - rules\n - website');
// Easter eggs
infoMessage(['ivefallenandicantgetup'], 'Stay right there, ' + user + "! Don't worry, help is on the way!");
infoMessage(['goddammitimpregnant'], '...for the fifteenth damn time!');
infoMessage(['yeah'], 'ｂｏｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉｉ');
infoMessage(['ohhi'], 'mark');
infoMessage(['poopity'], 'scoop');
switch (input) {
case 'fact':
case 'randomfact':
// Sends a random fact
request('https://spreadsheets.google.com/feeds/list/1ggvma51cj7ryPqfxGv47ZPLuP72keZmFbGE-KBHqbuU/4/public/values?alt=json', function(error, response, body) {
let boi = body;
let output = JSON.parse(boi);
let options = {
min: 0,
max: 11,
integer: true
};
let randomNumber = rn(options);
sendMessage(output["feed"]["entry"][randomNumber]["gsx$randomfact"]["$t"]);
});
break;
case 'randomquote':
// Sends a random quote
if (args.length !== 2) {
request('https://spreadsheets.google.com/feeds/list/1ggvma51cj7ryPqfxGv47ZPLuP72keZmFbGE-KBHqbuU/1/public/values?alt=json', function(error, response, body) {
let output = JSON.parse(body);
let options = {
min: 0,
max: output["feed"]["entry"].length,
integer: true
};
let randomNumber = rn(options);
sendMessage(('"' + output["feed"]["entry"][randomNumber]["gsx$quote"]["$t"] + '" - ' + output["feed"]["entry"][randomNumber]["gsx$teacherquoted"]["$t"] + ", " + output["feed"]["entry"][randomNumber]["gsx$date"]["$t"]))
});
} else {
console.log("SPECIFICS TEACHER");
let requestedTeacher = args[1];
request('https://spreadsheets.google.com/feeds/list/1ggvma51cj7ryPqfxGv47ZPLuP72keZmFbGE-KBHqbuU/1/public/values?alt=json', function (error, response, body) {
let quotes = JSON.parse(body);
console.log(quotes);
request('https://spreadsheets.google.com/feeds/list/1ggvma51cj7ryPqfxGv47ZPLuP72keZmFbGE-KBHqbuU/2/public/values?alt=json', function (error, response, body){
let ranges = JSON.parse(body);
console.log(ranges);
let teachers = [];
for (i = 0; i < ranges["feed"]["entry"].length; i++){
teachers.push(ranges["feed"]["entry"][i]["gsx$teacher"]["$t"]);
}
let teacherStart = [];
for (i = 0; i < ranges["feed"]["entry"].length; i++){
teacherStart.push(ranges["feed"]["entry"][i]["gsx$rangestart"]["$t"]);
}
let teacherEnd = [];
for (i = 0; i < ranges["feed"]["entry"].length; i++){
teacherEnd.push(ranges["feed"]["entry"][i]["gsx$rangeend"]["$t"]);
}
let requestedTeacherId = teachers.indexOf(requestedTeacher);
let requestedStart = teacherStart[requestedTeacherId];
let requestedEnd = teacherEnd[requestedTeacherId];
console.log(requestedStart);
console.log(requestedEnd);
let randomNumber = randomIntInc(requestedStart, requestedEnd);
console.log(requestedTeacher);
console.log(randomNumber);
});
});
}
break;
}
if (!valid && !['fact', 'randomfact', 'randomquote'].includes(input)) {
sendMessage('Invalid command. Type "!command" for a list of commands.');
}
} else
if (user !== 'teacher-quotes-bot' && channelID === '465330717782441986') {
let validQuoteRegex = /".+"\s-\s\w+,\s\d{2}\/\d{2}\/\d{4}/;
if (validQuoteRegex.test(message)) { // If the message sent was a valid quote
let justMessage = message.split('"')[1];
let justTeacher = message.split('"')[2].substring(3, message.split('"')[2].length - 12);
let justDate = message.substring(message.length - 10, message.length);
if (justTeacher.indexOf("(") > -1) {
justTeacher = justTeacher.substring(0, justTeacher.indexOf("("));
}
sendMessage("Message: " + justMessage + "\nTeacher: " + justTeacher + "\nDate: " + justDate);
} else {
sendMessage("Invalid Quote");
}
}
});

Answer 1

It appears the returned JSON is storing the values assigned to requestedStart and requestedEnd as strings rather than numbers. If that is the case, you will need to convert them to numbers before performing the arithmetic for the random number range.
function randomIntInc(low, high) {
console.log({
low,
high,
'(high - low) + 1': (high - low) + 1,
'(high - low + 1) + low': (high - low + 1) + low
});
return Math.floor(Math.random() * (high - low + 1) + low);
}
console.log({
strings: randomIntInc('10', '20'),
numbers: randomIntInc(10, 20)
});
Stepping through the string invocation, '10' and '20', results in the following operations:
('20' - '10' + 1): the order of operations will cause the subtraction operations to be done first which will automatically convert both strings to numbers and result in 10. The final addition will simply add the two number and produce 11.
The key part is the last addition which attempts to add a number with a string. This will cause the number, '11', to be converted to a string and then concatenated with the string, '10', which results in '1110'. This can be confusing unless you remember that the addition symbol is also used for string concatenation.
Finally the multiplication uses the random number times a string value of '1110' which results in a value of 0 - 11.1.