var natspec = require('natspec');

var natspecExpression = "Will multiply `a` by 7 and return `a * 7`.";
var call = {
    method: 'multiply',
    abi: abi,
    transaction: transaction
};

var evaluatedExpression = natspec.evaluateExpression(natspecExpression, call);
console.log(evaluatedExpression); // "Will multiply 4 by 7 and return 28."