如何与和评估结合使用，而不与结合使用？

Question

var stats = { a:1, b:2, c:3 };
with( stats )
{
    console.log( eval( "(a+b)*2" ) );
};

Greetings, I want to be able to perform an eval only within the scope of an object like above, but without using with. I have seen everywhere that its a major no-no to use with :|

Its just an example and we don't know what expression is in eval nor the object.

Answer 1

One possible way:

keys = Object.keys;
values = function(obj) { return keys(obj).map(function(k) {
    return obj[k]
})};

var stats = { a:1, b:2, c:3 };
expr = 'a+b*c'
fun = Function.apply(null, keys(stats).concat('return (' + expr + ')'))
result = fun.apply(null, values(stats))

console.log(result) // 7

The same as a reusable function:

evalWith = function(context, expr) {
    return Function.apply(
        null, Object.keys(context).concat('return (' + expr + ')')
    ).apply(null, Object.keys(context).map(function(k) {
        return context[k]
    }));
}

var stats = { a:1, b:2, c:3 };
result = evalWith(stats, 'a+b*c');

Using eval :

evalWith = function(context, expr) {
    return eval(Object.keys(context).map(function(k) {
        return "var " + k + "= context." + k;
    }).concat(expr).join(";"));
}