Wrap the compiled js_of_ocaml with a function (here I called it OCamlLoader()), load some dependencies and then load the OCaml

stub.js

let HACL = HaclLoader();

let sha256_init = HACL._Hacl_SHA2_256_init;
let sha256_update = HACL._Hacl_SHA2_256_update;
let sha256_finish = HACL._Hacl_SHA2_256_finish;

let state
let state_buffer
let message
let message_buffer
let hash
let hash_buffer

let sizeof_blake2b_state = function(s) {
    console.log('sizeof_blake2b_state');
    return 0;
}
let sizeof_secp256k1_num = function(s) {
    console.log('sizeof_secp256k1_num');
    return 0;
}
let caml_fill_bigstring = function(val, val_ofs, val_len, val_byte) {
    console.log('ml_secp256k1_fe_const_bytecode');
    // Fill val_buf with val_byte
    for (let i = 0; i < val_len; i++) {
	val.data[i + val_ofs] = val_byte;
    }
}
let ml_secp256k1_fe_const_bytecode = function(argv, argn) {
    console.log('ml_secp256k1_fe_const_bytecode');
    console.log(argv);
    for (let i = 0; i < 9; i++) {
	console.log(argv.data[i]);
    }
    console.log('argn: ' + argn);
    return 0;
}
let ml_secp256k1_ge_of_fields = function(s) {
    console.log('ml_secp256k1_ge_of_fields');
    return 0;
}
let uECC_curve_stub = function(s) {
    console.log('uECC_curve_stub');
    return 0;
}
let uECC_curve_private_key_stub = function(s) {
    console.log('uECC_curve_private_key_stub');
    return 0;
}
let uECC_curve_private_key_size_stub = function(s) {
    console.log('uECC_curve_private_key_size_stub');
    return 0;
}
let uECC_curve_public_key_size_stub = function(s) {
    console.log('uECC_curve_public_key_size_stub');
    return 0;
}
let ml_Hacl_SHA2_256_init = HACL._Hacl_SHA2_256_init;
let ml_Hacl_SHA2_256_update = HACL._Hacl_SHA2_256_update;
let ml_Hacl_SHA2_256_update_last = HACL._Hacl_SHA2_256_update_last;
let ml_Hacl_SHA2_256_finish = HACL._Hacl_SHA2_256_finish;

HACL.onRuntimeInitialized = function() {
    // Load secp256k1 wasm
    // Load uECC wasm

    OCamlLoader();
};