var result = (function(n) {

    // It can't read the variable because we didn't specify that it should take arguments.

    return (Function)('var n = n || 2; return n;')(n);

})(1);

​

console.log(result); // 2

​

// To specify that it should take arguments the first string is the parameters and the second string is the function body.

var result = (function(n) {

    return (Function)('n', 'return n;')(n);

})(1);

​

console.log(result); // 1