diff --git a/src/eckey.js b/src/eckey.js
index 23722d3..dc4cc17 100644
--- a/src/eckey.js
+++ b/src/eckey.js
@@ -63,7 +63,7 @@ ECKey.prototype.getPub = function(compressed) {
  * @deprecated Reserved keyword, factory pattern. Use toHex, toBytes, etc.
  */
 ECKey.prototype['export'] = function(format) {
-    format || (format = 'hex')
+    var format = format || 'hex'
     return this['to' + format.substr(0, 1).toUpperCase() + format.substr(1)]()
 }
 
@@ -77,7 +77,7 @@ ECKey.version_bytes = {
 }
 
 ECKey.prototype.toWif = function(version) {
-    var version = version || Network.mainnet.addressVersion;
+    version = version || Network.mainnet.addressVersion;
 
     return base58.checkEncode(this.toBytes(), ECKey.version_bytes[version])
 }
@@ -147,7 +147,7 @@ ECPubKey.prototype.multiply = function(key) {
 }
 
 ECPubKey.prototype['export'] = function(format) {
-    format || (format = 'hex')
+    var format = format || 'hex';
     return this['to' + format.substr(0, 1).toUpperCase() + format.substr(1)]()
 }
 
@@ -165,7 +165,7 @@ ECPubKey.prototype.toBin = function() {
 }
 
 ECPubKey.prototype.toWif = function(version) {
-    var version = version || Network.mainnet.addressVersion;
+    version = version || Network.mainnet.addressVersion;
 
     return base58.checkEncode(this.toBytes(), version)
 }
@@ -173,7 +173,7 @@ ECPubKey.prototype.toWif = function(version) {
 ECPubKey.prototype.toString = ECPubKey.prototype.toHex
 
 ECPubKey.prototype.getAddress = function(version) {
-    var version = version || Network.mainnet.addressVersion;
+    version = version || Network.mainnet.addressVersion;
 
     return new Address(util.sha256ripe160(this.toBytes()), version);
 }
diff --git a/src/opcode.js b/src/opcode.js
index 6fc8aad..0db2604 100644
--- a/src/opcode.js
+++ b/src/opcode.js
@@ -1,4 +1,4 @@
-Opcode = {
+var Opcode = {
     map: {
         // push value
         OP_0         : 0,
diff --git a/src/transaction.js b/src/transaction.js
index d01a920..a0c9760 100644
--- a/src/transaction.js
+++ b/src/transaction.js
@@ -60,8 +60,9 @@ Transaction.prototype.addInput = function (tx, outIndex) {
         return this.addInput(args[0], args[1]);
     }
     else {
-        var hash = typeof tx === "string" ? tx : tx.hash
-        var hash = Array.isArray(hash) ? convert.bytesToHex(hash) : hash
+        var hash = typeof tx === "string" ? tx : tx.hash;
+        hash = Array.isArray(hash) ? convert.bytesToHex(hash) : hash;
+
         this.ins.push(new TransactionIn({
             outpoint: {
                 hash: hash,
@@ -269,7 +270,9 @@ Transaction.deserialize = function(buffer) {
     }
     obj.version = readAsInt(4);
     var ins = readVarInt();
-    for (var i = 0; i < ins; i++) {
+    var i;
+
+    for (i = 0; i < ins; i++) {
         obj.ins.push({
             outpoint: {
                 hash: convert.bytesToHex(readBytes(32).reverse()),
@@ -280,12 +283,14 @@ Transaction.deserialize = function(buffer) {
         });
     }
     var outs = readVarInt();
-    for (var i = 0; i < outs; i++) {
+
+    for (i = 0; i < outs; i++) {
         obj.outs.push({
             value: convert.bytesToNum(readBytes(8)),
             script: new Script(readVarString())
         });
     }
+
     obj.locktime = readAsInt(4);
 
     return new Transaction(obj);