JSFiddle - React, Tailwind, and code Playground

HTML

<span id="result"></span>

JavaScript

// Define subroutine to do one sample test.
function sample() {
  // Fill an array with zeros so ++ works.
	const results = new Array(6);
  for (let i = 0; i < 6; i++) {
    results[i] = 0;
  }

  // Roll 14 dice and bin results.
	let die;
  for (let i = 0; i < 14; i++) {
    die = Math.floor(Math.random() * 6);
    results[die]++;
  }

  if (results[0] === 7 ) {
    // This does not count.
    return false;
  }

  // Determine if the number of 1s plus any other adds to 7
  for (let j = 1; j < 6; j++) {
    if (results[0] + results[j] === 7 ) {
      return true;
    }
  }
  return false;
}

let trials = 0;
let successes = 0;

// Run some trials and then render the result.
function sampleMany() {
  for (let j = 0; j < 10000; j++) {
    trials++;
    if (sample()) {
      successes++;
    }
  }
  const rate = (successes / trials).toFixed(6);
  document.getElementById('result').innerHTML = `Rate ${rate} in ${trials} trials`;
}

// Need to use a callback to show progress.
for (let i = 0; i < 1000; i++) {
	setTimeout(sampleMany,0);
}