用Javascript创建一个可以访问局部变量的类

Question

I'm working on a debugger that injects code into already existing code. Which then use eval() to log and run it.

However eval() seems to work in only its existing scope. To overcome this I tried to add a class that i recreated in each local scope. But it doesnt work.

I've added code to ilustrate my problem. The first alert works as expected, I'm assuming that it is because MyClass is created in the same scope.

The second alert still display b as 10 even though I've set b in local scope to 20 inside the TestC function. And the last alert doesn't work at all eval() returns in console "Uncaught ReferenceError: c is not defined".

If I add the whole MyClass inside each function and the assign it, then it works, but that doesn't feel like an elegant solution. And can add 1000's of lines of code to a project.

http://jsfiddle.net/ekim/zryj3taq/2/

var MyClass = function()
{
    this.MyAlert = function(codex)
    {
        eval(codex);
    }
}

var b = 10;
var MyOne = new MyClass();
MyOne.MyAlert("alert(b);");

function TestC()
{
    var b = 20;
    var MyOne2 = new MyClass();
    MyOne2.MyAlert("alert(b);");

    var c = 20;
    var MyOne2 = new MyClass();
    MyOne2.MyAlert("alert(c);");
}


TestC();

Answer 1

You can use new Function(\\[arg1\\[, arg2\\[, ...argN\\]\\],\\] functionBody)

 (function(){ var str = "return (A+B)*C"; var myFunc = new Function("A","B","C", str); var result = myFunc(2,3,4); console.log(result); }()); /* Example with function */ (function(){ var fncDouble = function (X) { return X*2; } var str = "return F(A)+B"; var myFunc = new Function("F","A","B", str); var result = myFunc(fncDouble,3,1); console.log(result); }()); 

Answer 2

据我所知，没有简单的解决方案，因为eval()函数只是创建一个新的单独的编译器。

Answer 3

试试这个： MyOne2.MyAlert.call(this, "alert(b)");