<label>Expression: <input id="expression" value="6 * 4 + 2 ^ 2" /></label>

<pre><code id="result"></code></pre>

<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjs/11.0.1/math.min.js" integrity="sha512-B82WLflI1EQiR9sGbIV1ddGVvK4ghj1xjMShL7YvcOrHjX2qP72lHztT1DxBVPiz1aTR6mOUJbtwj06uadL2GA==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

<script type="module">

  const input = document.getElementById('expression');

  const output = document.getElementById('result');

​

  function evaluate () {

    const expression = input.value.trim();

    let result;

​

    try {

      result = math.evaluate(expression);

    }

    catch (ex) {

      if (ex instanceof Error) result = ex.toString();

      else throw ex;

    }

​

    output.textContent = result;

  }

​

  input.addEventListener('input', evaluate);

  evaluate();

</script>

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