compute.ts

function calcExpression(left, operator, right) {
  let result;
  switch (operator) {
    case '+':
      result = +new Big(left).plus(right);
      break;
    case '-':
      result = +new Big(left).minus(right);
      break;
    case '*':
      result = +new Big(left).times(right);
      break;
    case '/':
      result = +new Big(left).div(right);
      break;
    case '%':
      result = +new Big(left).mod(right);
      break;
    case '>>':
      result = left >> right;
      break;
    case '>>>':
      result = left >>> right;
      break;
    case '<<':
      result = left << right;
      break;
    case '|':
      result = left | right;
      break;
    case '&':
      result = left & right;
      break;
    case '^':
      result = left ^ right;
      break;
    case '**':
      let i = right;
      while (--i) {
        result = result || left;
        result = +new Big(result).times(left);
      }
      break;
    default:
  }
  return result;
}

function computeNode(node: ASTNode) {
  let left;
  let right;
  if (node.left.value) left = node.left.value;
  else if (node.left.type === 'BinaryExpression') {
    left = computeNode(node.left);
  }
  if (node.right.value) right = node.right.value;
  else if (node.right.type === 'BinaryExpression') {
    right = computeNode(node.right);
  }
  return calcExpression(left, node.operator, right);
}