diff --git a/src/transaction_builder.js b/src/transaction_builder.js
index 023591a..05c0591 100644
--- a/src/transaction_builder.js
+++ b/src/transaction_builder.js
@@ -15,164 +15,7 @@ function TransactionBuilder() {
   this.tx = new Transaction()
 }
 
-TransactionBuilder.prototype.addInput = function(prevTx, index, sequence, prevOutScript) {
-  var prevOutHash
-
-  if (typeof prevTx === 'string') {
-    prevOutHash = new Buffer(prevTx, 'hex')
-
-    // TxId hex is big-endian, we want little-endian hash
-    Array.prototype.reverse.call(prevOutHash)
-
-  } else if (prevTx instanceof Transaction) {
-    prevOutHash = prevTx.getHash()
-    prevOutScript = prevTx.outs[index].script
-
-  } else {
-    prevOutHash = prevTx
-
-  }
-
-  var prevOutType
-  if (prevOutScript !== undefined) {
-    prevOutType = scripts.classifyOutput(prevOutScript)
-
-    assert.notEqual(prevOutType, 'nonstandard', 'PrevOutScript not supported (nonstandard)')
-  }
-
-  assert(this.signatures.every(function(input) {
-    return input.hashType & Transaction.SIGHASH_ANYONECANPAY
-  }), 'No, this would invalidate signatures')
-
-  var prevOut = prevOutHash.toString('hex') + ':' + index
-  assert(!(prevOut in this.prevOutMap), 'Transaction is already an input')
-
-  var vout = this.tx.addInput(prevOutHash, index, sequence)
-  this.prevOutMap[prevOut] = true
-  this.prevOutScripts[vout] = prevOutScript
-  this.prevOutTypes[vout] = prevOutType
-
-  return vout
-}
-
-TransactionBuilder.prototype.addOutput = function(scriptPubKey, value) {
-  assert(this.signatures.every(function(signature) {
-    return (signature.hashType & 0x1f) === Transaction.SIGHASH_SINGLE
-  }), 'No, this would invalidate signatures')
-
-  return this.tx.addOutput(scriptPubKey, value)
-}
-
-TransactionBuilder.prototype.sign = function(index, privKey, redeemScript, hashType) {
-  assert(this.tx.ins.length >= index, 'No input at index: ' + index)
-  hashType = hashType || Transaction.SIGHASH_ALL
-
-  var prevOutScript = this.prevOutScripts[index]
-  var prevOutType = this.prevOutTypes[index]
-
-  var scriptType, hash
-  if (redeemScript) {
-    prevOutScript = prevOutScript || scripts.scriptHashOutput(redeemScript.getHash())
-    prevOutType = prevOutType || 'scripthash'
-
-    assert.equal(prevOutType, 'scripthash', 'PrevOutScript must be P2SH')
-
-    scriptType = scripts.classifyOutput(redeemScript)
-
-    assert.notEqual(scriptType, 'scripthash', 'RedeemScript can\'t be P2SH')
-    assert.notEqual(scriptType, 'nonstandard', 'RedeemScript not supported (nonstandard)')
-
-    hash = this.tx.hashForSignature(index, redeemScript, hashType)
-
-  } else {
-    prevOutScript = prevOutScript || privKey.pub.getAddress().toOutputScript()
-    scriptType = prevOutType || 'pubkeyhash'
-
-    assert.notEqual(scriptType, 'scripthash', 'PrevOutScript requires redeemScript')
-
-    hash = this.tx.hashForSignature(index, prevOutScript, hashType)
-  }
-
-  if (!(index in this.signatures)) {
-    this.signatures[index] = {
-      hashType: hashType,
-      pubKeys: [],
-      redeemScript: redeemScript,
-      scriptType: scriptType,
-      signatures: []
-    }
-  }
-
-  var input = this.signatures[index]
-  assert.equal(input.hashType, hashType, 'Inconsistent hashType')
-  assert.deepEqual(input.redeemScript, redeemScript, 'Inconsistent redeemScript')
-
-  var signature = privKey.sign(hash)
-  input.pubKeys.push(privKey.pub)
-  input.signatures.push(signature)
-}
-
-TransactionBuilder.prototype.build = function() {
-  return this.__build(false)
-}
-
-TransactionBuilder.prototype.buildIncomplete = function() {
-  return this.__build(true)
-}
-
-TransactionBuilder.prototype.__build = function(allowIncomplete) {
-  if (!allowIncomplete) {
-    assert(this.tx.ins.length > 0, 'Transaction has no inputs')
-    assert(this.tx.outs.length > 0, 'Transaction has no outputs')
-    assert(this.signatures.length > 0, 'Transaction has no signatures')
-    assert.equal(this.signatures.length, this.tx.ins.length, 'Transaction is missing signatures')
-  }
-
-  var tx = this.tx.clone()
-
-  // Create script signatures from signature meta-data
-  this.signatures.forEach(function(input, index) {
-    var scriptSig
-    var scriptType = input.scriptType
-
-    var signatures = input.signatures.map(function(signature) {
-      return signature.toScriptSignature(input.hashType)
-    })
-
-    switch (scriptType) {
-      case 'pubkeyhash':
-        var signature = signatures[0]
-        var pubKey = input.pubKeys[0]
-        scriptSig = scripts.pubKeyHashInput(signature, pubKey)
-
-        break
-
-      case 'multisig':
-        var redeemScript = allowIncomplete ? undefined : input.redeemScript
-        scriptSig = scripts.multisigInput(signatures, redeemScript)
-
-        break
-
-      case 'pubkey':
-        var signature = signatures[0]
-        scriptSig = scripts.pubKeyInput(signature)
-
-        break
-
-      default:
-        assert(false, scriptType + ' not supported')
-    }
-
-    if (input.redeemScript) {
-      scriptSig = scripts.scriptHashInput(scriptSig, input.redeemScript)
-    }
-
-    tx.setInputScript(index, scriptSig)
-  })
-
-  return tx
-}
-
+// Static constructors
 TransactionBuilder.fromTransaction = function(transaction) {
   var txb = new TransactionBuilder()
 
@@ -255,4 +98,163 @@ TransactionBuilder.fromTransaction = function(transaction) {
   return txb
 }
 
+// Operations
+TransactionBuilder.prototype.addInput = function(prevTx, index, sequence, prevOutScript) {
+  var prevOutHash
+
+  if (typeof prevTx === 'string') {
+    prevOutHash = new Buffer(prevTx, 'hex')
+
+    // TxId hex is big-endian, we want little-endian hash
+    Array.prototype.reverse.call(prevOutHash)
+
+  } else if (prevTx instanceof Transaction) {
+    prevOutHash = prevTx.getHash()
+    prevOutScript = prevTx.outs[index].script
+
+  } else {
+    prevOutHash = prevTx
+
+  }
+
+  var prevOutType
+  if (prevOutScript !== undefined) {
+    prevOutType = scripts.classifyOutput(prevOutScript)
+
+    assert.notEqual(prevOutType, 'nonstandard', 'PrevOutScript not supported (nonstandard)')
+  }
+
+  assert(this.signatures.every(function(input) {
+    return input.hashType & Transaction.SIGHASH_ANYONECANPAY
+  }), 'No, this would invalidate signatures')
+
+  var prevOut = prevOutHash.toString('hex') + ':' + index
+  assert(!(prevOut in this.prevOutMap), 'Transaction is already an input')
+
+  var vout = this.tx.addInput(prevOutHash, index, sequence)
+  this.prevOutMap[prevOut] = true
+  this.prevOutScripts[vout] = prevOutScript
+  this.prevOutTypes[vout] = prevOutType
+
+  return vout
+}
+
+TransactionBuilder.prototype.addOutput = function(scriptPubKey, value) {
+  assert(this.signatures.every(function(signature) {
+    return (signature.hashType & 0x1f) === Transaction.SIGHASH_SINGLE
+  }), 'No, this would invalidate signatures')
+
+  return this.tx.addOutput(scriptPubKey, value)
+}
+
+TransactionBuilder.prototype.build = function() {
+  return this.__build(false)
+}
+
+TransactionBuilder.prototype.buildIncomplete = function() {
+  return this.__build(true)
+}
+
+TransactionBuilder.prototype.__build = function(allowIncomplete) {
+  if (!allowIncomplete) {
+    assert(this.tx.ins.length > 0, 'Transaction has no inputs')
+    assert(this.tx.outs.length > 0, 'Transaction has no outputs')
+    assert(this.signatures.length > 0, 'Transaction has no signatures')
+    assert.equal(this.signatures.length, this.tx.ins.length, 'Transaction is missing signatures')
+  }
+
+  var tx = this.tx.clone()
+
+  // Create script signatures from signature meta-data
+  this.signatures.forEach(function(input, index) {
+    var scriptSig
+    var scriptType = input.scriptType
+
+    var signatures = input.signatures.map(function(signature) {
+      return signature.toScriptSignature(input.hashType)
+    })
+
+    switch (scriptType) {
+      case 'pubkeyhash':
+        var signature = signatures[0]
+        var pubKey = input.pubKeys[0]
+        scriptSig = scripts.pubKeyHashInput(signature, pubKey)
+
+        break
+
+      case 'multisig':
+        var redeemScript = allowIncomplete ? undefined : input.redeemScript
+        scriptSig = scripts.multisigInput(signatures, redeemScript)
+
+        break
+
+      case 'pubkey':
+        var signature = signatures[0]
+        scriptSig = scripts.pubKeyInput(signature)
+
+        break
+
+      default:
+        assert(false, scriptType + ' not supported')
+    }
+
+    if (input.redeemScript) {
+      scriptSig = scripts.scriptHashInput(scriptSig, input.redeemScript)
+    }
+
+    tx.setInputScript(index, scriptSig)
+  })
+
+  return tx
+}
+
+TransactionBuilder.prototype.sign = function(index, privKey, redeemScript, hashType) {
+  assert(this.tx.ins.length >= index, 'No input at index: ' + index)
+  hashType = hashType || Transaction.SIGHASH_ALL
+
+  var prevOutScript = this.prevOutScripts[index]
+  var prevOutType = this.prevOutTypes[index]
+
+  var scriptType, hash
+  if (redeemScript) {
+    prevOutScript = prevOutScript || scripts.scriptHashOutput(redeemScript.getHash())
+    prevOutType = prevOutType || 'scripthash'
+
+    assert.equal(prevOutType, 'scripthash', 'PrevOutScript must be P2SH')
+
+    scriptType = scripts.classifyOutput(redeemScript)
+
+    assert.notEqual(scriptType, 'scripthash', 'RedeemScript can\'t be P2SH')
+    assert.notEqual(scriptType, 'nonstandard', 'RedeemScript not supported (nonstandard)')
+
+    hash = this.tx.hashForSignature(index, redeemScript, hashType)
+
+  } else {
+    prevOutScript = prevOutScript || privKey.pub.getAddress().toOutputScript()
+    scriptType = prevOutType || 'pubkeyhash'
+
+    assert.notEqual(scriptType, 'scripthash', 'PrevOutScript requires redeemScript')
+
+    hash = this.tx.hashForSignature(index, prevOutScript, hashType)
+  }
+
+  if (!(index in this.signatures)) {
+    this.signatures[index] = {
+      hashType: hashType,
+      pubKeys: [],
+      redeemScript: redeemScript,
+      scriptType: scriptType,
+      signatures: []
+    }
+  }
+
+  var input = this.signatures[index]
+  assert.equal(input.hashType, hashType, 'Inconsistent hashType')
+  assert.deepEqual(input.redeemScript, redeemScript, 'Inconsistent redeemScript')
+
+  var signature = privKey.sign(hash)
+  input.pubKeys.push(privKey.pub)
+  input.signatures.push(signature)
+}
+
 module.exports = TransactionBuilder