binding gl.compressTexImage2D

[sleep2death]

Hi Dominic,
I've decided to bind the 'gl.compressTexImage2D' function which was marked as EJ_BIND_FUNCTION_NOT_IMPLEMENTED, and this is my implement:

EJ_BIND_FUNCTION(compressedTexImage2D, ctx, argc, argv) {
    if( argc != 7 ) { return NULL; }

    scriptView.currentRenderingContext = renderingContext;
    EJ_UNPACK_ARGV(GLenum target, GLint level, GLenum internalformat);
 ...
        EJ_UNPACK_ARGV_OFFSET(3, GLsizei width, GLsizei height, GLint border);

        if( JSValueIsObject(ctx, argv[6]) ) {
             NSMutableData *data = JSObjectGetTypedArrayData(ctx, (JSObjectRef)argv[6]);
            NSLog(@"upload array data");
             //something **WRONG** here: function JSObjectGetTypedArrayData  returned a NULL OBJECT
            void *pixels = data.mutableBytes;

            glCompressedTexImage2D(target, level, internalformat, width, height, border, size, pixels);

        }
...

    return NULL;
}

I use pixi-compressed-textures to upload the compressed texture, it handled the mipmap already:

this.generateWebGLTexture = function (gl, preserveSource) {
        ...
        // Loop through each mip level of compressed texture data provided and upload it to the given texture.
        for (var i = 0; i < this.levels; ++i) {
            // Determine how big this level of compressed texture data is in bytes.
            var levelSize = textureLevelSize(this.internalFormat, width, height);
            // Get a view of the bytes for this level of DXT data.
            var dxtLevel = new Uint8Array(this.data.buffer, this.data.byteOffset + offset, levelSize);
            // Upload!
            gl.compressedTexImage2D(gl.TEXTURE_2D, i, this.internalFormat, width, height, 0, dxtLevel);
...
};

How can I get the correct compressed data from javascript?
Thanks!