emscripten webgl 2 errors

foo.cpp

#define GL_GLEXT_PROTOTYPES
#include <GLES/gl.h>
#include <GLES/glext.h>
#include <GLES3/gl3.h>
#include <stdio.h>
#include <emscripten.h>
#include <emscripten/html5.h>

#define GL_CALL( x ) \
    { \
        x; \
        GLenum error = glGetError(); \
        if( error != GL_NO_ERROR ) \
            printf( "GL ERROR: %d,  %s\n", (int)error, #x ); \
    } \


int main()
{
    emscripten_set_canvas_size( 100, 100 );

    EmscriptenWebGLContextAttributes attrs;
    emscripten_webgl_init_context_attributes(&attrs);

    attrs.enableExtensionsByDefault = 1;
    attrs.majorVersion = 2;
    attrs.minorVersion = 0;

    EMSCRIPTEN_WEBGL_CONTEXT_HANDLE context = emscripten_webgl_create_context( 0, &attrs );
    emscripten_webgl_make_context_current(context);

    EM_BOOL enabled = emscripten_webgl_enable_extension( context, "EXT_texture_filter_anisotropic" );
    printf("anisotropy enabled: %d\n", enabled);


    // Anisotropy
    //
    GLfloat maxAnisotropy;
    GL_CALL( glGetFloatv(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &maxAnisotropy) );
    printf("max anisotropy: %f\n", maxAnisotropy);


    // Vertex Arrays
    //
    GLuint vao1;
    GL_CALL( glGenVertexArrays( 1, &vao1 ) );
    GL_CALL( glBindVertexArray( vao1 ) );
    printf( "vao1: %d\n", vao1 );

    GLint vao2;
    GL_CALL( glGetIntegerv( GL_VERTEX_ARRAY_BINDING, &vao2 ) );
    printf( "vao2: %d\n", vao2 );


    // Sampler Objects
    //
    GLuint sampler;
    GL_CALL( glGenSamplers( 1, &sampler ) );
    GL_CALL( glSamplerParameteri( sampler, GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, (int)maxAnisotropy ) );

    GL_CALL( glBindSampler( 0, sampler ) );

    GLint sampler2;
    GL_CALL( glGetIntegerv( GL_SAMPLER_BINDING, &sampler2 ) );
    printf( "sampler2: %d\n", sampler2 );



  return 0;
}