# Trouble with New() function when using Emscripten
**URL:** https://discourse.vtk.org/t/trouble-with-new-function-when-using-emscripten/3080
**Category:** Development
**Created:** [April 17, 2020, 12:22pm UTC](https://discourse.vtk.org/t/trouble-with-new-function-when-using-emscripten/3080 "2020-04-17T12:22:00Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@claretb](https://discourse.vtk.org/u/claretb)
#### Post date: [April 17, 2020, 12:22pm UTC](https://discourse.vtk.org/t/trouble-with-new-function-when-using-emscripten/3080/1 "2020-04-17T12:22:01Z")
I’m trying to port my project to WebAssembly with Emscripten. I used [this](https://github.com/dicehub/VTK/tree/emscripten) source of VTK and some external libraries. And when I compiling a test project, I get the following warnings:
```
warning: undefined symbol: _ZN15vtkImageStencil3NewEv
warning: undefined symbol: _ZN16vtkImageYBRToRGB3NewEv
.
.
.
```
These warnings cause errors on browser and caused by New() functions. For example this:
`static vtkImageStencil *New();`
using:
`vtkImageStencil* imageStencil = vtkImageStencil::New();`
So what do you think about this problem? What can I do?
cc: @Sebastien_Jourdain @thewtex
---
### Author:  [@thewtex](https://discourse.vtk.org/u/thewtex)
#### Post date: [April 17, 2020, 1:43pm UTC](https://discourse.vtk.org/t/trouble-with-new-function-when-using-emscripten/3080/2 "2020-04-17T13:43:00Z")
@claretb this is likely an issue with the CMake configuration. To address this, use [itk.js](https://insightsoftwareconsortium.github.io/itk-js/) to prepare the project with a standard CMake configuration, and first verify that you can build it with a native C++ toolchain.
---
### Author:  [@claretb](https://discourse.vtk.org/u/claretb)
#### Post date: [April 19, 2020, 7:57am UTC](https://discourse.vtk.org/t/trouble-with-new-function-when-using-emscripten/3080/3 "2020-04-19T07:57:45Z")
@thewtex
> [@thewtex](#):
>
> this is likely an issue with the CMake configuration.
Yes, I thought like you. And I checked many times this configurations. But I cannot find any solution for my problem.
> [@thewtex](#):
>
> To address this, use [itk.js](https://insightsoftwareconsortium.github.io/itk-js/) to prepare the project with a standard CMake configuration
I have a lot of questions about itk.js.
- We made some changes and additions in VTK and GDCM. Also we have a special library that uses them and OpenCV. So, How can I import this libraries to itk.js?
- I want to create instance on JS side because our project requires this. And I cannot found an example of this type. How can I use Emscripten bindings with itk.js?
- How can we add or change Emscripten flags at itk.js?
- Can we use builded js files without `runPipelineBrowser`?