Question

Technologies:

javascript

Tolerim

3 hours ago

What is the method for obtaining the value of a local variable within a function when using Jint?

How can I retrieve the value of a locally defined variable in a JavaScript function using Jint in C#? The JavaScript code, "testStr," is provided as a string, and I am not responsible for its dynamic generation and modification. Here's an example:

var globalVar = 5;

function myFunc(a, b) {

    var localVar1 = { "Hello" : 987 };

    var localVar2 = a + b;

    return;
}

Additionally, here is the C# code:

jintEngine.Execute(testStr);

// the following method does not exist in Jint, but is included here as an example...
var valueStr = jintEngine.GoToFunc("myFunc").GetValue("localVar1").ToString();

How can I obtain the string value of localVar1? Thank you!

Answers(1)

Accepted Answer

Unfortunately, it is not directly possible to access local variables from outside the function in JavaScript. However, one way to accomplish something similar is to modify the JavaScript function to return the desired local variable, then capture the return value in C#. Here's an example: JavaScript code:

var globalVar = 5;

function myFunc(a, b) {
    var localVar1 = { "Hello" : 987 };
    var localVar2 = a + b;
    return localVar1;
}

C# code using Jint:

var engine = new Jint.Engine();
var result = engine.Execute(@"
    var globalVar = 5;
    function myFunc(a, b) {
        var localVar1 = { 'Hello': 987 };
        var localVar2 = a + b;
        return localVar1;
    }
    myFunc(1, 2);
").GetCompletionValue();
var localVar1 = result.GetOwnProperty("Hello").Value;

In this example, we modified the JavaScript function to return localVar1. Then we executed the JavaScript with Jint and captured the return value in a C# JsValue object using the GetCompletionValue() method. Finally, we extracted the value of localVar1 from the JsValue object using the GetOwnProperty() method. Note that you'll need to modify the C# code to handle cases where localVar1 might not be defined or might have a different type.