Evaluate a mathjs expression and return the result

evaluate-math-expression.js

/**
 * Evaluates a mathjs expression and returns the result
 * @param expr A Math.js (https://mathjs.org/) compatible exression string
 * @returns A Promise that resolves to the result of the math expression
 */
export async function evaluateMathExpressionWithMathJs(expr: string): Promise<number> {
  /**
   * Loads the Math.js library dynamically and returns a promise
   * that resolves when the library is loaded.  Currently not possible
   * to load as ESM, see https://github.com/josdejong/mathjs/issues/1841
   */
  function loadMathJs(): Promise<void> {
    return new Promise((resolve, reject) => {
      if (window.math) {
        resolve();
        return;
      }

      const script = document.createElement('script');
      script.src =
        'https://cdn.jsdelivr.net/npm/[email protected]/lib/browser/math.min.js';
      script.onload = () => {
        window.math = math;
        resolve();
      };
      script.onerror = () => {
        reject(new Error('Failed to load Math.js library'));
      };

      document.head.appendChild(script);
    });
  }

  try {
    await loadMathJs();
  
    return math.evaluate(expr);
  } catch(err) {
    throw new Error(`Unable to evaluate expression "${expr}" with mathjs: ${err.message}`);
  }
}