Multiple functions in my Javascript file

[fallais]

Hello, I come from Otto world and I want to migrate to this library because of very bad performance issues. I am using it for a normalisation pipeline.

I used to put 4 or 5 functions into a JS file, and then call one of them into my Golang code.

Example (here I call the function Exlcude) :

// Run
returnRaw, err := vm.Run(`Exclude(` + string(incidentJSON) + `);`)
if err != nil {
	return false, fmt.Errorf("Error while running the JS code : %s", err)
}

How can I do this with your lib please ? Thanks a lot ! :)

[dop251]

Hi @fallais,

Assuming that you have run the code that defines the Exclude function, you can do the following:

exclude, _ := goja.AssertFunction(vm.Get("Exclude"))

returnRaw, err := exclude(nil, vm.ToValue(string(incidentJSON))
// note, res will be a goja.Value, if you need a native Go value you need to export it:
v := returnRaw.Export()

Hope this helps.

[fallais]

Thanks a lot !
But it is not working, it is not finding the function..

Here is the code, it should find it..

// Exclude returns true if the incident is excluded. Otherwise it must return false.
var Exclude = function(incident){
   ...
}

[fallais]

I do not set the script file anywhere.. that is the issue I guess.. ^^

        // Create the VM
	vm := goja.New()

	// Set the variables
	vm.Set("customer", customer)
	vm.Set("incident", incidentJSON)

	// Run
	excludeFunc, ok := goja.AssertFunction(vm.Get("Exclude"))
	if !ok {
		return false, fmt.Errorf("Error while asserting the function [Exclude]: %s", err)
	}
	returnRaw, err := excludeFunc(nil, vm.ToValue(string(incidentJSON)))
	if err != nil {
		return false, fmt.Errorf("Error while executing the function [Exclude]: %s", err)
	}

	excluded := returnRaw.ToBoolean()

PS : do I really need to marshall into JSON ? Does the lib do it automatically when passing struct into the VM ?

[dop251]

I can't see you are running anything that could define the Exclude function. Do you expect it to appear in the vm by magic? :)

[fallais]

Yes, I realized it... But I do not understand the logic here. I have to get a Callable in order to run the function I defined in the source file. But to get it, I need to run it into the VM. But I can't run it because is has no parameter..

So, if I understand correctly, I ned to run it one first time for "nothing" ?

[dop251]

You don't run the function, you run the code that defines the function.

[fallais]

Something like this ?

// Marshal incident as JSON object
	incidentJSON, err := json.Marshal(incident)
	if err != nil {
		return false, fmt.Errorf("Error while marshalling the incident : %s", err)
	}

	// Create the VM
	vm := goja.New()

	// Set the variables
	vm.Set("customer", customer)
	vm.Set("incident", incidentJSON)

	// Run the script
	_, err = vm.RunString(norm.script)
	if err != nil {
		return false, fmt.Errorf("Error while running the JS code: %s", err)
	}

	// Run
	excludeFunc, ok := goja.AssertFunction(vm.Get("Exclude"))
	if !ok {
		return false, fmt.Errorf("Error while asserting the function [Exclude]: %s", err)
	}
	returnRaw, err := excludeFunc(nil, vm.ToValue(string(incidentJSON)))
	if err != nil {
		return false, fmt.Errorf("Error while executing the function [Exclude]: %s", err)
	}

	excluded := returnRaw.ToBoolean()

[dop251]

Something like this:

vm := goja.New()
_, err = vm.RunString("function Exclude(incident) { ... your code here ... }")
if err != nil {
	return false, fmt.Errorf("Error while running the JS code: %s", err)
}

// Run
excludeFunc, ok := goja.AssertFunction(vm.Get("Exclude"))
if !ok {
	return false, fmt.Errorf("Error while asserting the function [Exclude]: %s", err)
}
returnRaw, err := excludeFunc(nil, vm.ToValue(string(incidentJSON)))
if err != nil {
	return false, fmt.Errorf("Error while executing the function [Exclude]: %s", err)
}

excluded := returnRaw.ToBoolean()

I'm not sure about the role of the customer variable and whether you need to set it as a global variable, rather than passing it as a parameter.

As for serialising into JSON, you can pass a Go variable directly (like vm.ToValue(incident)), however bear in mind that it will wrap it into a js "host" object so it will not behave exactly as a native JS value. If you don't need to modify it inside your javascript function it should be ok.

[fallais]

Perfect thanks :)

[fallais]

Well, I have errors with the indexOf : TypeError: Cannot read property 'indexOf' of undefined at

But the description field does exists, so the indexOf should work.. It may be because of the host object type ?

[fallais]

If I use JSON.parse() inside the JS function to parse the object, it seems to be working. But I need to marshal it of course. If I do not marshal it and do not use the JSON.parse(), not working.

[dop251]

I can't really help you without seeing a full test case, sorry.