txbuilder: refactor for clarity

src/transaction_builder.js

@@ -371,22 +371,20 @@ TransactionBuilder.prototype.sign = function (index, privKey, redeemScript, hash
   var signatureScript = input.redeemScript || input.prevOutScript
   var signatureHash = this.tx.hashForSignature(index, signatureScript, hashType)
 
+  // enforce signature order matches public keys
   if (input.scriptType === 'multisig' && input.redeemScript && input.signatures.length !== input.pubKeys.length) {
-    // store signatures locally
-    var _signatures = input.signatures.slice()
-
-    // loop over pubKeys to set their respective signature or set it to OP_0
     input.signatures = input.pubKeys.map(function (pubKey) {
-      var signature = null
-      _signatures.forEach(function (_signature, _sigIdx) {
-        // check if the signature is not null / false / OP_0 and verify if it belongs to the pubKey
-        if (!signature && _signature && pubKey.verify(signatureHash, _signature)) {
-          // use .splice to remove the signature from the list, so we won't verify it again
-          signature = _signatures.splice(_sigIdx, 1)[0]
-        }
+      var match
+
+      // check for any matching signatures
+      input.signatures.some(function (signature) {
+        if (!pubKey.verify(signatureHash, signature)) return false
+        match = signature
+
+        return true
       })
 
-      return signature || ops.OP_0
+      return match || undefined
     })
   }