@spacemesh/sm-codec

// Import
import { Stdtemplates, StdPublicKeys, StdMethods } from '@spacemesh/sm-codec';
import ed25519 from '@spacemesh/ed25519-wasm';

// SingleSig example
(async () => {
  // Get SingleSig template
  const singleSig = StdTemplates[StdPublicKeys.SingleSig];
  // Get method
  const spawnTpl = singleSig.methods[StdMethods.Spawn];

  // Prepare SpawnPayload
  const spawnPayload = {
    Arguments: {
      PublicKey: Uint8Array.from([/* your public key: 32 bytes */]),
    },
  };
  // Calculate Principal address (of your new account)
  const principal = spawnTpl.principal(spawnPayload);
  // Encode SpawnTransaction
  const rawTx = spawnTpl.encode(principal, spawnPayload);
  // Get transaction hash, it is used in signing
  const txHash = hash(rawTx);
  // Then use `ed25519` library to sign the hash with your private key
  const sig = ed25519.sign(myPrivateKey, txHash);
  // And finally sign tx (actualy it concatenates bytes)
  const signedTx = spawnTpl.sign(rawTx, sig);

  // Note: Principal method exists on any method
  // So this example will work as well:
  singleSig.methods[StdMethods.Spend].principal(spawnPayload);

})();

import { PublicKey, SingleSig, Codecs } from '@spacemesh/sm-codec';
import { Struct, str } from 'scale-ts';

const spawnCodec = Struct({
  Owner: PublicKey,
});
const saySmthCodec = Struct({
  message: str,
})

// Address of the template in the network
// 24 bytes length
const address = Uint8Array.from([
  0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 100,
]);

// Creating own templates
const spawnTpl = new Transaction({
  address,
  methodSelector: 0,
  spawnArgsCodec: spawnCodec,
  // For Spawn transaction it is neccessary to add a template address into payload
  payloadCodec: withTemplateAddress(address, spawnCodec),
  sigCodec: SingleSig,
});

const saySmthTpl =
  new Transaction({
    address,
    methodSelector: 1,
    spawnArgsCodec: spawnCodec,
    payloadCodec: saySmthCodec,
    sigCodec: SingleSig,
  });

// Use as in examples above
const principal = saySmthTpl.principal({
  Owner: Uint8Array.from([ /* 32 bytes  */ ]),
});

const rawTx = saySmthTpl.encode(principal, {
  message: 'hello world',
});

})();