diff --git a/.gitignore b/.gitignore
index 2e8c1ec..0a221d4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -33,8 +33,5 @@ jspm_packages
 # Editors
 .idea
 
-# Lib
-lib
-
 # others
-.DS_Store
\ No newline at end of file
+.DS_Store
diff --git a/README.md b/README.md
index 321c0b5..989594f 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,15 @@
 
 This is a very simple version of a compiler expression evaluation. It can be used for parsing expressions without introducing the risk of script injection via `eval` method.
 
+# Submission
+
+For now we always should include updated prebuilt code into the repository. As for now for quick development we include this npm module directly as git repository.
+
+To do so, run before commit:
+```sh
+npm run prepublish
+```
+
 # Commands
 
 - `npm run clean` - Remove `lib/` directory
diff --git a/lib/index.js b/lib/index.js
new file mode 100644
index 0000000..1b2039e
--- /dev/null
+++ b/lib/index.js
@@ -0,0 +1 @@
+'use strict';var _createClass=function(){function a(a,b){for(var c,d=0;d<b.length;d++)c=b[d],c.enumerable=c.enumerable||!1,c.configurable=!0,'value'in c&&(c.writable=!0),Object.defineProperty(a,c.key,c)}return function(b,c,d){return c&&a(b.prototype,c),d&&a(b,d),b}}();Object.defineProperty(exports,'__esModule',{value:!0});exports.evaluate=evaluate,exports.getFieldNamesFromExpression=getFieldNamesFromExpression,exports.populatePreparedConditions=populatePreparedConditions;var _lodash=require('lodash'),_lodash2=_interopRequireDefault(_lodash);function _interopRequireDefault(a){return a&&a.__esModule?a:{default:a}}function _classCallCheck(a,b){if(!(a instanceof b))throw new TypeError('Cannot call a class as a function')}var Stack=function(){function a(){_classCallCheck(this,a),this.top=-1,this.items=[]}return _createClass(a,[{key:'push',value:function push(a){var b=this.top;this.items[b+1]=a,this.top=b+1}},{key:'pop',value:function pop(){var a=this.top,b=this.items[a];return this.top=a-1,b}},{key:'peek',value:function peek(){return this.items[this.top]}},{key:'empty',value:function empty(){return-1===this.top}}]),a}(),precedence={"(":8,")":8,"!":7,"^":6,"*":5,"/":5,"+":4,"-":4,contains:3,hasLength:3,">":3,"<":3,"==":2,"!=":2,"&&":1,"||":1};function hasPrecedence(a,b){return'('!==b&&')'!==b&&precedence[b]>=precedence[a]}function applyOp(c,d,e){switch(c){case'+':return e+d;case'-':return e-d;case'*':return e*d;case'/':return e/d;case'==':return e===d;case'!=':return e!==d;case'&&':return e&&d;case'||':return e||d;case'>':return e>d;case'<':return e<d;case'!':return!d;case'contains':try{var a=JSON.parse(d);return _lodash2.default.some(e||[],a)}catch(a){return-1<(e||[]).indexOf(d)}case'hasLength':return(e||[]).length===d;}return 0}var allowedOps=['+','-','*','/','==','!=','&&','||','>','<','contains','hasLength','!'],oneParamOps=['!'],opsSplitters=['\\s+','\\(','\\)','!(?!=)'],splitRegexp=new RegExp('('+opsSplitters.join('|')+')');function evaluate(a,b){for(var c=a.split(splitRegexp).map(function(a){return a.trim()}).filter(function(a){return''!==a}),d=new Stack,e=new Stack,f=[],g=0;g<c.length;g++)if('('===c[g])e.push(c[g]),f.push(g);else if(')'===c[g]){for(;'('!==e.peek()&&!e.empty();){var h=e.pop();-1===oneParamOps.indexOf(h)?d.push(applyOp(h,d.pop(),d.pop())):d.push(applyOp(h,d.pop()))}e.empty()?f.push(g):(f.pop(),e.pop())}else if(-1<allowedOps.indexOf(c[g])){for(;!e.empty()&&hasPrecedence(c[g],e.peek());){var i=e.pop();-1===oneParamOps.indexOf(i)?d.push(applyOp(i,d.pop(),d.pop())):d.push(applyOp(i,d.pop()))}e.push(c[g])}else if(c[g]in b)d.push(_lodash2.default.get(b,c[g]));else if(!isNaN(c[g]))d.push(parseInt(c[g]));else{var j=c[g].replace(/'/g,'');j='true'===j||'false'!==j&&j,d.push(j)}if(0!==f.length)throw new Error('Parens with the following token indexes are unbalanced: '+f);for(;!e.empty();){var k=e.pop();-1===oneParamOps.indexOf(k)?d.push(applyOp(k,d.pop(),d.pop())):d.push(applyOp(k,d.pop()))}return d.pop()}function getFieldNamesFromExpression(a){var b=/([a-z]+[a-z0-9]*(?:\.[a-z]+[a-z0-9]*)+)/ig,c=void 0,d=[];do c=b.exec(a),c&&d.push(c[1]);while(c);return d}function populatePreparedConditions(a,b){return b&&_lodash2.default.forEach(b,function(b,c){var d=new RegExp('('+'^|\\s|\\(|!'+')'+c+'(?='+'$|\\s|\\)'+')','g');a=a.replace(d,'$1'+b)}),a}
\ No newline at end of file
diff --git a/lib/index.spec.js b/lib/index.spec.js
new file mode 100644
index 0000000..ce6ee6d
--- /dev/null
+++ b/lib/index.spec.js
@@ -0,0 +1 @@
+'use strict';var _chai=require('chai'),_chai2=_interopRequireDefault(_chai),_index=require('./index');function _interopRequireDefault(a){return a&&a.__esModule?a:{default:a}}_chai2.default.should();var testData={text:'string',textEmpty:'',a:1,stringa:'1',b:2,c:3,d:-1,zero:0,someArray:[1,2,3],someArrayWithText:['a','b','c'],f:!1,t:!0,nestedObject:{textProperty:'test',PREPARED_CONDITION_1:'fake prepared condition property',propertyWithObject:{PREPARED_CONDITION_2:'fake prepared condition property'}}},preparedConditions={PREPARED_CONDITION_1:'(someArray hasLength 3)',PREPARED_CONDITION_2:'((someArrayWithText contains \'a\') || (someArrayWithText contains \'b\'))'};describe('Evaluate: ',function(){describe('operator',function(){it('hasLength (true)',function(){var a=(0,_index.evaluate)('someArray hasLength 3',testData);a.should.equal(!0)}),it('hasLength (false)',function(){var a=(0,_index.evaluate)('someArray hasLength 4',testData);a.should.equal(!1)}),it('!false => true',function(){var a=(0,_index.evaluate)('!f',testData);a.should.equal(!0)}),it('!true => false',function(){var a=(0,_index.evaluate)('!t',testData);a.should.equal(!1)}),it('! with conditions',function(){var a=(0,_index.evaluate)('!t || !f',testData);a.should.equal(!0)}),it('!textEmpty => true',function(){var a=(0,_index.evaluate)('!textEmpty',testData);a.should.equal(!0)}),it('!text => false',function(){var a=(0,_index.evaluate)('!text',testData);a.should.equal(!1)}),it('== (true)',function(){var a=(0,_index.evaluate)('f == f',testData);a.should.equal(!0)}),it('== (false)',function(){var a=(0,_index.evaluate)('f == t',testData);a.should.equal(!1)}),it('!= (true)',function(){var a=(0,_index.evaluate)('f != t',testData);a.should.equal(!0)}),it('!= (false)',function(){var a=(0,_index.evaluate)('f != f',testData);a.should.equal(!1)})}),describe('logical operators',function(){it('test plain conditions',function(){var a=(0,_index.evaluate)('(someArrayWithText contains \'a\' || someArrayWithText contains \'d\')',testData);a.should.equal(!0)}),it('contains \'a\' && hasLength (true)',function(){var a=(0,_index.evaluate)('(someArrayWithText contains \'a\') && (someArrayWithText hasLength 3)',testData);a.should.equal(!0)}),it('contains \'a\' || contains \'b\'',function(){var a=(0,_index.evaluate)('someArrayWithText contains \'d\' && someArrayWithText contains \'b\'',testData);a.should.equal(!1)}),it('contains \'a\' && hasLength (true) && contains \'b\'',function(){var a=(0,_index.evaluate)('someArrayWithText contains \'a\' && someArrayWithText hasLength 3 && someArrayWithText contains \'b\'',testData);a.should.equal(!0)}),it('contains \'a\' && hasLength (false)',function(){var a=(0,_index.evaluate)('(someArrayWithText contains \'a\') && (someArrayWithText hasLength 2)',testData);a.should.equal(!1)}),it('contains \'a\' && hasLength (false) && contains \'b\'',function(){var a=(0,_index.evaluate)('((someArrayWithText contains \'a\') && (someArrayWithText hasLength 1) && (someArrayWithText contains \'b\'))',testData);a.should.equal(!1)})}),describe('expression format',function(){it('no spaces near parenthesis',function(){var a=(0,_index.evaluate)('someArray contains (a + b) * 2',testData);a.should.equal(!1)}),it('no spaces near parenthesis with conditions',function(){var a=(0,_index.evaluate)('(someArrayWithText contains \'a\') || (someArrayWithText contains \'b\') || (someArrayWithText contains \'c\')',testData);a.should.equal(!0)}),xit('multiple spaces',function(){var a=(0,_index.evaluate)('someArray  contains  (  b  -  a  )  *  2',testData);a.should.equal(!0)})}),describe('+ operator',function(){it('should do simple addition',function(){var a=(0,_index.evaluate)('a + b',testData);a.should.equal(testData.a+testData.b)}),xit('should be read as separate from other tokens even if there are no spaces in between',function(){var a=(0,_index.evaluate)('a+b',testData);a.should.equal(testData.a+testData.b)}),xit('should identify signs in numbers',function(){var a=(0,_index.evaluate)('- a + ( + b)',testData);a.should.equal(-testData.a+testData.b)}),it('should be commutative',function(){var a=(0,_index.evaluate)('a + b',testData),b=(0,_index.evaluate)('b + a',testData);a.should.equal(b)}),it('should be associative',function(){var a=(0,_index.evaluate)('a + (b + c)',testData),b=(0,_index.evaluate)('(a + b) + c',testData);a.should.equal(b)}),it('should be distributive',function(){var a=(0,_index.evaluate)('a * (b + c)',testData),b=(0,_index.evaluate)('(a * b) + (a * c)',testData);a.should.equal(b)}),it('should have additive identity',function(){var a=(0,_index.evaluate)('a + 0',testData);a.should.equal(testData.a)}),xit('should return same if an argument is null',function(){var a=(0,_index.evaluate)('a + null',testData);a.should.equal(testData.a)}),xit('should return NaN if an argument is undefined',function(){var a=(0,_index.evaluate)('a + undefined',testData);a.should.be.NaN}),xit('should return NaN if an argument is NaN',function(){var a=(0,_index.evaluate)('a + NaN',testData);a.should.be.NaN}),it('should add true to numbers',function(){var a=(0,_index.evaluate)('t + 5',testData);a.should.equal(6)})}),describe('- operator',function(){it('should do simple subtraction',function(){var a=(0,_index.evaluate)('a - b',testData);a.should.equal(testData.a-testData.b)}),xit('should be read as separate from other tokens even if there are no spaces in between',function(){var a=(0,_index.evaluate)('a-b',testData);a.should.equal(testData.a-testData.b)}),it('should be distributive',function(){var a=(0,_index.evaluate)('a * (b - c)',testData),b=(0,_index.evaluate)('(a * b) - (a * c)',testData);a.should.equal(b)}),it('should have additive identity',function(){var a=(0,_index.evaluate)('a - 0',testData);a.should.equal(testData.a)}),xit('should return 0 if an argument is null',function(){var a=(0,_index.evaluate)('a - null',testData);a.should.equal(testData.a)}),it('should return NaN if an argument is undefined',function(){var a=(0,_index.evaluate)('a - undefined',testData);a.should.be.NaN}),it('should return NaN if an argument is NaN',function(){var a=(0,_index.evaluate)('a - NaN',testData);a.should.be.NaN}),it('should subtract true from numbers',function(){var a=(0,_index.evaluate)('f - 5',testData);a.should.equal(-5)})}),describe('* operator',function(){it('should do simple multiplication',function(){var a=(0,_index.evaluate)('a * b',testData);a.should.equal(testData.a*testData.b)}),xit('should be read as separate from other tokens even if there are no spaces in between',function(){var a=(0,_index.evaluate)('a*b',testData);a.should.equal(testData.a*testData.b)}),xit('should identify signs',function(){var a=(0,_index.evaluate)('a * (- b)',testData);a.should.equal(testData.a*-testData.b)}),it('should be commutative',function(){var a=(0,_index.evaluate)('a * b',testData),b=(0,_index.evaluate)('b * a',testData);a.should.equal(b)}),it('should be associative',function(){var a=(0,_index.evaluate)('a * (b * c)',testData),b=(0,_index.evaluate)('(a * b) * c',testData);a.should.equal(b)}),it('should have multiplicative identity',function(){var a=(0,_index.evaluate)('b * 1',testData);a.should.equal(testData.b)}),xit('should return 0 if an argument is null',function(){var a=(0,_index.evaluate)('a * null',testData);a.should.equal(0)}),it('should return NaN if an argument is undefined',function(){var a=(0,_index.evaluate)('a * undefined',testData);a.should.be.NaN}),it('should return NaN if an argument is NaN',function(){var a=(0,_index.evaluate)('a * NaN',testData);a.should.be.NaN}),xit('should flip the sign of Infinity',function(){var a=(0,_index.evaluate)('d * Infinity',testData);a.should.equal(-Infinity)}),it('should return NaN when multiplying 0 and Infinity',function(){var a=(0,_index.evaluate)('0 * Infinity',testData);isNaN(a).should.equal(!0)})}),describe('/ operator',function(){it('should do simple division',function(){var a=(0,_index.evaluate)('a / b',testData);a.should.equal(testData.a/testData.b)}),xit('should be read as separate from other tokens even if there are no spaces in between',function(){var a=(0,_index.evaluate)('a/b',testData);a.should.equal(testData.a*testData.b)}),it('should return Infinity when dividing be 0',function(){var a=(0,_index.evaluate)('a / 0',testData);a.should.equal(Infinity)}),xit('should identify sign in its arguments',function(){var a=(0,_index.evaluate)('- a / b',testData);a.should.equal(-testData.a/testData.b)}),it('should take precedence over addition and subtraction',function(){var a=(0,_index.evaluate)('a + b / c - d * b',testData);a.should.equal(testData.a+testData.b/testData.c-testData.d*testData.b)}),xit('should return 0 when dividing by Infinity',function(){var a=(0,_index.evaluate)('a / Infinity',testData);a.should.equal(0)}),it('should do 0 / 0 == NaN',function(){var a=(0,_index.evaluate)('0 / 0',testData);isNaN(a).should.equal(!0)}),it('should do Infinity / Infinity == NaN',function(){var a=(0,_index.evaluate)('Infinity / Infinity',testData);isNaN(a).should.equal(!0)}),xit('should return Infinity if an argument is null',function(){var a=(0,_index.evaluate)('a / null',testData);a.should.equal(0)}),it('should return NaN if an argument is undefined',function(){var a=(0,_index.evaluate)('a / undefined',testData);a.should.be.NaN}),it('should return NaN if an argument is NaN',function(){var a=(0,_index.evaluate)('a / NaN',testData);a.should.be.NaN})}),describe('== operator',function(){xit('should compare NaNs',function(){var a=(0,_index.evaluate)('NaN == NaN',testData);a.should.equal(!1)}),xit('should compare Infinities',function(){var a=(0,_index.evaluate)('Infinity == Infinity',testData);a.should.equal(!0)}),it('should compare nulls',function(){var a=(0,_index.evaluate)('null == null',testData);a.should.equal(!0)}),it('should compare undefined',function(){var a=(0,_index.evaluate)('undefined == undefined',testData);a.should.equal(!0)}),it('should compare boolean true',function(){var a=(0,_index.evaluate)('t == true',testData);a.should.equal(!0)}),it('should compare boolean false',function(){var a=(0,_index.evaluate)('f == false',testData);a.should.equal(!0)}),it('should compare string and number',function(){var a=(0,_index.evaluate)('stringa == a',testData);a.should.equal(!1)}),xit('should compare boolean and number',function(){var a=(0,_index.evaluate)('zero == f',testData);a.should.equal(!0)})}),describe('!= operator',function(){xit('should compare NaNs',function(){var a=(0,_index.evaluate)('NaN != NaN',testData);a.should.equal(!0)}),xit('should compare Infinities',function(){var a=(0,_index.evaluate)('Infinity != Infinity',testData);a.should.equal(!1)}),it('should compare nulls',function(){var a=(0,_index.evaluate)('null != null',testData);a.should.equal(!1)}),it('should compare undefined',function(){var a=(0,_index.evaluate)('undefined != undefined',testData);a.should.equal(!1)}),it('should compare string and number',function(){var a=(0,_index.evaluate)('stringa != a',testData);a.should.equal(!0)}),it('should compare inequality for boolean true',function(){var a=(0,_index.evaluate)('t != true',testData);a.should.equal(!1)}),it('should compare inequality for boolean false',function(){var a=(0,_index.evaluate)('f != false',testData);a.should.equal(!1)}),xit('should compare boolean and number',function(){var a=(0,_index.evaluate)('zero != f',testData);a.should.equal(!1)})}),describe('&& operator',function(){it('true && true => true',function(){var a=(0,_index.evaluate)('t && t',testData);a.should.equal(!0)}),it('true && false => false',function(){var a=(0,_index.evaluate)('t && f',testData);a.should.equal(!1)}),it('false && true => false',function(){var a=(0,_index.evaluate)('f && t',testData);a.should.equal(!1)}),it('false && false => false',function(){var a=(0,_index.evaluate)('f && f',testData);a.should.equal(!1)})}),describe('|| operator',function(){it('true || true => true',function(){var a=(0,_index.evaluate)('t || t',testData);a.should.equal(!0)}),it('true || false => true',function(){var a=(0,_index.evaluate)('t || f',testData);a.should.equal(!0)}),it('false || true => true',function(){var a=(0,_index.evaluate)('f || t',testData);a.should.equal(!0)}),it('false || false => false',function(){var a=(0,_index.evaluate)('f || f',testData);a.should.equal(!1)})}),describe('parser',function(){it('should parse literal constants like numbers',function(){var a=(0,_index.evaluate)('4 + 2',testData);a.should.equal(6)}),it('should throw error if one opening parenthesis is unbalanced',function(){try{(0,_index.evaluate)('((someArrayWithText contains \'a\') || (someArrayWithText contains \'b\') || (someArrayWithText contains \'c\')',testData)}catch(a){a.message.should.equal('Parens with the following token indexes are unbalanced: 0')}}),it('should throw error if multiple opening parenthesis are unbalanced',function(){try{(0,_index.evaluate)('(someArrayWithText contains \'a\') || ((someArrayWithText contains \'b\') || ((someArrayWithText contains \'c\')',testData)}catch(a){a.message.should.equal('Parens with the following token indexes are unbalanced: 6,13')}}),it('should throw error if one closing parenthesis is unbalanced',function(){try{(0,_index.evaluate)('(someArrayWithText contains \'a\')) || (someArrayWithText contains \'b\') || (someArrayWithText contains \'c\')',testData)}catch(a){a.message.should.equal('Parens with the following token indexes are unbalanced: 5')}}),it('should throw error if multiple closing parenthesis are unbalanced',function(){try{(0,_index.evaluate)('(someArrayWithText contains \'a\') || (someArrayWithText contains \'b\')) || (someArrayWithText contains \'c\'))',testData)}catch(a){a.message.should.equal('Parens with the following token indexes are unbalanced: 11,18')}}),xit('should parse literal constants like numbers with decimal numbers',function(){var a=(0,_index.evaluate)('4.2 + 2.3',testData);a.should.equal(4.2+2.3)}),xit('should parse literal constants like booleans',function(){var a=(0,_index.evaluate)('true && true',testData);a.should.equal(!0)}),xit('should treat unknown variables as undefined',function(){var a=(0,_index.evaluate)('unknownVariable',testData);a.should.be.undefined})}),describe('! operator',function(){it('!true => false',function(){var a=(0,_index.evaluate)('!t',testData);a.should.equal(!1)}),it('!false => true',function(){var a=(0,_index.evaluate)('!f',testData);a.should.equal(!0)}),xit('!undefined => true',function(){var a=(0,_index.evaluate)('!undefined',testData);a.should.equal(!0)}),xit('!null => true',function(){var a=(0,_index.evaluate)('! null',testData);a.should.equal(!0)})}),describe('> operator',function(){it('should compare numbers',function(){var a=(0,_index.evaluate)('a > b',testData);a.should.equal(testData.a>testData.b)}),it('should compare strings',function(){var a=(0,_index.evaluate)('\'absfd\' > \'fsb\'',testData);a.should.equal(!1)}),it('should compare numbers and strings',function(){var a=(0,_index.evaluate)('\'absfd\' > 1',testData);a.should.equal(!1)}),it('should compare undefined',function(){var a=(0,_index.evaluate)('undefined > 1',testData);a.should.equal(1<void 0)}),it('should compare null',function(){var a=(0,_index.evaluate)('null > 1',testData);a.should.equal(!1)}),it('should compare NaN',function(){var a=NaN,b=(0,_index.evaluate)('NaN > 1',testData);b.should.equal(1<a)})}),describe('< operator',function(){it('should compare numbers',function(){var a=(0,_index.evaluate)('a < b',testData);a.should.equal(testData.a<testData.b)}),it('should compare strings',function(){var a=(0,_index.evaluate)('\'absfd\' < \'fsb\'',testData);a.should.equal(!0)}),it('should compare numbers and strings',function(){var a=(0,_index.evaluate)('\'absfd\' < 1',testData);a.should.equal(!1)}),it('should compare undefined',function(){var a=(0,_index.evaluate)('undefined < 1',testData);a.should.equal(1>void 0)}),xit('should compare null',function(){var a=(0,_index.evaluate)('null < 1',testData);a.should.equal(!0)}),it('should compare NaN',function(){var a=NaN,b=(0,_index.evaluate)('NaN < 1',testData);b.should.equal(1>a)})})}),describe('Replace prepared conditions: ',function(){it('should replace single prepared condition',function(){var a=(0,_index.populatePreparedConditions)('PREPARED_CONDITION_1',preparedConditions);a.should.equal(preparedConditions.PREPARED_CONDITION_1)}),it('should replace multiple prepared conditions',function(){var a=(0,_index.populatePreparedConditions)('PREPARED_CONDITION_1 && PREPARED_CONDITION_2',preparedConditions);a.should.equal(preparedConditions.PREPARED_CONDITION_1+' && '+preparedConditions.PREPARED_CONDITION_2)}),it('should not replace prepared condition inside text literals',function(){var a=(0,_index.populatePreparedConditions)('someArray contains \'PREPARED_CONDITION_1\' && a == PREPARED_CONDITION_2',preparedConditions);a.should.equal('someArray contains \'PREPARED_CONDITION_1\' && a == '+preparedConditions.PREPARED_CONDITION_2)}),it('should not replace prepared condition inside object properties level 1',function(){var a=(0,_index.populatePreparedConditions)('nestedObject.PREPARED_CONDITION_1 && a == PREPARED_CONDITION_2',preparedConditions);a.should.equal('nestedObject.PREPARED_CONDITION_1 && a == '+preparedConditions.PREPARED_CONDITION_2)}),it('should not replace prepared condition inside object properties level 2',function(){var a=(0,_index.populatePreparedConditions)('nestedObject.propertyWithObject.PREPARED_CONDITION_1 && a == PREPARED_CONDITION_2',preparedConditions);a.should.equal('nestedObject.propertyWithObject.PREPARED_CONDITION_1 && a == '+preparedConditions.PREPARED_CONDITION_2)}),it('should not replace prepared condition in the part of another prepared condition variable',function(){var a=(0,_index.populatePreparedConditions)('SUFFIX_PREPARED_CONDITION_2 && PREPARED_CONDITION_2 && PREPARED_CONDITION_2_POSTFIX',preparedConditions);a.should.equal('SUFFIX_PREPARED_CONDITION_2 && '+preparedConditions.PREPARED_CONDITION_2+' && PREPARED_CONDITION_2_POSTFIX')}),it('should not replace prepared condition delimited by parentheses',function(){var a=(0,_index.populatePreparedConditions)('(PREPARED_CONDITION_2)',preparedConditions);a.should.equal('('+preparedConditions.PREPARED_CONDITION_2+')')}),it('should not replace prepared condition delimited preceded by "!"',function(){var a=(0,_index.populatePreparedConditions)('!PREPARED_CONDITION_2',preparedConditions);a.should.equal('!'+preparedConditions.PREPARED_CONDITION_2)})});
\ No newline at end of file
diff --git a/src/index.js b/src/index.js
index 2c1aa49..0ca5ed2 100644
--- a/src/index.js
+++ b/src/index.js
@@ -163,13 +163,17 @@ export function evaluate(expression, data) {
   // Stack for Operators: 'ops'
   const ops = new Stack();
 
+  // Keep track of unbalanced parenthesis
+  const unbalancedParens = [];
+
   for (let i = 0; i < tokens.length; i++) {
     if (tokens[i] === '(') {
       ops.push(tokens[i]);
+      unbalancedParens.push(i);
 
       // Closing brace encountered, solve expression since the last opening brace
     } else if (tokens[i] === ')') {
-      while (ops.peek() !== '(') {
+      while (ops.peek() !== '(' && !ops.empty()) {
         const op = ops.pop();
         if (oneParamOps.indexOf(op) !== -1) {
           values.push(applyOp(op, values.pop()));
@@ -177,7 +181,13 @@ export function evaluate(expression, data) {
           values.push(applyOp(op, values.pop(), values.pop()));
         }
       }
-      ops.pop();// removing opening brace
+      // if the ops array is empty means there is an unbalanced closing parenthesis
+      if (ops.empty()) {
+        unbalancedParens.push(i);
+      } else {
+        unbalancedParens.pop();
+        ops.pop(); // removing opening brace
+      }
 
       // Current token is an operator.
     } else if (allowedOps.indexOf(tokens[i]) > -1) {
@@ -213,6 +223,12 @@ export function evaluate(expression, data) {
       }
     }
   }
+
+  // if there are unbalanced parenthesis throw an error
+  if (unbalancedParens.length !== 0) {
+    throw new Error(`Parens with the following token indexes are unbalanced: ${unbalancedParens}`);
+  }
+
   // debugger
   // Parsed expression tokens are pushed to values/ops respectively,
   // Running while loop to evaluate the expression
diff --git a/src/index.spec.js b/src/index.spec.js
index 9066f6d..54eefa3 100644
--- a/src/index.spec.js
+++ b/src/index.spec.js
@@ -558,6 +558,46 @@ describe('Evaluate: ', () => {
       res.should.equal(4 + 2);
     });
 
+    it('should throw error if one opening parenthesis is unbalanced', () => {
+      const expression = `((someArrayWithText contains 'a') || (someArrayWithText contains 'b') || (someArrayWithText contains 'c')`;
+
+      try {
+        evaluate(expression, testData);
+      } catch (error) {
+        error.message.should.equal('Parens with the following token indexes are unbalanced: 0');
+      }
+    });
+
+    it('should throw error if multiple opening parenthesis are unbalanced', () => {
+      const expression = `(someArrayWithText contains 'a') || ((someArrayWithText contains 'b') || ((someArrayWithText contains 'c')`;
+
+      try {
+        evaluate(expression, testData);
+      } catch (error) {
+        error.message.should.equal('Parens with the following token indexes are unbalanced: 6,13');
+      }
+    });
+
+    it('should throw error if one closing parenthesis is unbalanced', () => {
+      const expression = `(someArrayWithText contains 'a')) || (someArrayWithText contains 'b') || (someArrayWithText contains 'c')`;
+
+      try {
+        evaluate(expression, testData);
+      } catch (error) {
+        error.message.should.equal('Parens with the following token indexes are unbalanced: 5');
+      }
+    });
+
+    it('should throw error if multiple closing parenthesis are unbalanced', () => {
+      const expression = `(someArrayWithText contains 'a') || (someArrayWithText contains 'b')) || (someArrayWithText contains 'c'))`;
+
+      try {
+        evaluate(expression, testData);
+      } catch (error) {
+        error.message.should.equal('Parens with the following token indexes are unbalanced: 11,18');
+      }
+    });
+
     xit('should parse literal constants like numbers with decimal numbers', () => {
       const res = evaluate('4.2 + 2.3', testData);
       res.should.equal(4.2 + 2.3);