get-expr-value.js

var expr = `(a.name == 'lsong' ? b : { c:2 }) + 30`;

const data = {
  a: {
    name: 'lsong'
  },
  b: 1,
};

const getValue = (expr, data) => {
  const args = Object.keys(data);
  const fn = Function.apply(null, args.concat(`return ${expr};`));
  return fn.apply(data, args.map(k => data[k]));
};

console.log(getValue(expr, data));