Javascript How To Concatenate Separate Characters Into One String In Array?

Question

I wrote a code for a "Heads or Tails" game below and:

var userInput = prompt("Enter maximum number output: ");

function coinFlip() {
  return (Math.floor(Math.random() * 2) === 0) ? 'Heads' ; 'Tails';
}

for (var i = 0; i < 6; i++)
{
  var result = [];

  result["randomNum"] = (Math.floor(Math.random()*userInput);

  result["coin"] = (coinFlip());
}

I'm trying to count the sum of total heads and sum of total tails each with the code:

var headsCount = 0;
var tailsCount = 0;

for (var j = 0; j < result["coin"].length; j++)
{
   if (result["coin"] == 'Heads')
      headsCount++;
   else
      tailsCount++;
}

The only problem is that it's counting each characters of 'Heads' and 'Tails' in the result["coin"] array as separate (such as 'H'-'e'-'a'-'d'-'s') and not into a full string (like "Heads"). Thus, instead of increment by 1 each time the loop above runs, it increments by +5.

I want it to increment by +1 only.

How do I make it so that the code reads the full string stored in result["coin"] and not character-by-character?

EDITED -- changed the <2 to *2

You have a lot of problems. var result = [] creates an empty array, but `result["coin"] does not add anything to the array :) See for yourself in the Chrome developers console. This is entirely independent of the problem at hand, but it's something basic you should know about. — Akshat Mahajan
– Akshat Mahajan, Commented Jul 11, 2016 at 2:48
What is this (Math.floor(Math.random() < 2) === 0) supposed to do? I think you probably want Math.random() < 0.5 ? 'Heads' : 'Tails' — jfriend00
– jfriend00, Commented Jul 11, 2016 at 2:49
The Math.floor(Math.random() < 2 ===0) ? 'Heads' ; 'Tails'; is supposed to just give a random 'Heads' or 'Tails' result everytime the loop runs. — 5120bee
– 5120bee, Commented Jul 11, 2016 at 2:53
@SpencerWieczorek - No need for you to answer that. The point of my comment was to ask the OP (not someone else) to examine that code and try to figure out what it does rather than just tell them (trying to get them to learn on their own). I know what it does and what they probably should do (as my comment shows). — jfriend00
– jfriend00, Commented Jul 11, 2016 at 2:53
Oh, we typed in at the same time. I didn't see your reply got entered first. — 5120bee
– 5120bee, Commented Jul 11, 2016 at 2:54

Rick Viscomi · Accepted Answer · 2016-07-11 03:07:29Z

1

var result = []; is inside the for loop, so it is being overwritten with an empty array each time. So when you try to loop over the results, there's one one item in it; the last one. Pull the result array out of the loop so that you can add to it in each iteration.

It seems userInput should be the number of times to loop. Not sure why you're putting it in result["randomNum"]. result is an array, not an object, so it only has integer keys.

Instead of adding the result of the coin toss to result["coin"] I think you mean to add it to the array, so after tossing it six times it might look like this: ["Heads", "Heads", "Tails", "Heads", "Tails", "Tails"]. You can do this by calling result.push with the coin toss output.

To get one of two results randomly, compare the output of Math.random() against 0.5, which is half way between the limits. Numbers less than 0.5 can be considered heads, while numbers greater than or equal to 0.5 can be considered tails.

Putting it all together, this is what I think you were going for:

function coinFlip() {
  return Math.random() < 0.5 ? 'Heads' : 'Tails';
}

var result = [];
var userInput = parseInt(prompt("Enter maximum number output: "), 10);
for (var i = 0; i < userInput; i++) {
  result.push(coinFlip());
}

var headsCount = 0;
var tailsCount = 0;

for (var j = 0; j < result.length; j++) {
  if (result[j] == 'Heads')
    headsCount++;
  else
    tailsCount++;
}

console.log(headsCount, "heads and", tailsCount, "tails");

All that being said, there are definitely areas for improvement. You don't need to loop once to build the results, then loop a second time to read the results.

You can count the number of heads/tails as the coins are flipped. For example:

function isCoinFlipHeads() {
  return Math.random() < 0.5;
}

var numFlips = parseInt(prompt("How many flips?"), 10);
var heads = 0;
var tails = 0;
for (var i = 0; i < numFlips; i++) {
  isCoinFlipHeads() ? heads++ : tails++;
}
console.log(heads, "heads and", tails, "tails");

answered Jul 11, 2016 at 3:07

Rick Viscomi

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2 Comments

5120bee Over a year ago

For the userInput,I wanted to take user input of any number they wish, generate a random number from 0 to the number they input, then display it in a result array. At the same time, I want to simulate a game of "Heads or Tails" and also display that result in the same result array. Here's a link to my full code: link

5120bee Over a year ago

Well, this wasn't quite what I was going for but your code did manage to help me understand things better and I modified your second function code a little bit for the part that I wanted. Thanks!

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