diff --git a/README.md b/README.md
index 4767f44..a460feb 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,16 @@ Options:
   -h --help         Show this.
 ~~~
 
+It also can be used inside node code
+
+~~~ text
+var tapDifflet = require('tap-difflet');
+
+var formatter = tapDifflet({
+  pessimistic: true // Only output failed tests. `false` by default.
+});
+~~~
+
 ## Output
 
 ![tap-difflet](http://i.imgur.com/8uFAvXU.png)
diff --git a/bin/tap-difflet b/bin/tap-difflet
index fb017c2..c6c2429 100755
--- a/bin/tap-difflet
+++ b/bin/tap-difflet
@@ -1,19 +1,5 @@
 #!/usr/bin/env node
 
-/* Modules */
-
-var parser    = require('tap-parser-yaml');
-var through   = require('through2');
-var duplexer  = require('duplexer');
-var hirestime = require('hirestime');
-var prettyms  = require('pretty-ms');
-var chalk     = require('chalk');
-var objdiff   = require('difflet')({
-  indent: 2,
-  comment: true
-}).compare;
-
-var ansidiff  = require('ansidiff');
 
 var docopt = require('docopt').docopt;
 
@@ -33,189 +19,18 @@ var options = docopt(usage, {
   version: pkg.version,
 });
 
-var tap = parser();
-var out = through();
-var dup = duplexer(tap, out);
-
-if (options['--pessimistic']) {
-  var anAssertFailed = true;
-  var originalOut = out;
-  var buffer = null;
-  tap.on('comment', function(comment) {
-    if (buffer && anAssertFailed) {
-      for (var bi=0; bi<buffer.length; ++bi) {
-        originalOut.push(buffer[bi]);
-      }
-    }
-
-    buffer = null;
-    anAssertFailed = false;
-    out = originalOut;
-
-    if (getCommentType(comment) === CommentType.OTHER) {
-      buffer = [];
-      out = buffer;
-    }
-  });
-
-  tap.on('assert', function(res) {
-    if (!res.ok) {
-      anAssertFailed = true;
-    }
+function getOptionsWithotDashes(options) {
+  const transformedOptions = {}
+  Object.keys(options).forEach(key => {
+    const keyWithoutDashes = key.replace(/^(--|-)/, '');
+    transformedOptions[keyWithoutDashes] = options[key];
   });
+  return transformedOptions;
 }
 
-/* Helpers */
-var CommentType = {
-  OTHER: 1,
-  TESTS: 2,
-  PASS: 3,
-  FAIL: 4,
-  OK: 5
-};
-
-function getCommentType(comment) {
-  if (/^tests\s+[0-9]+$/gi.test(comment)) {
-    return CommentType.TESTS;
-  }
-  else if (/^pass\s+[0-9]+$/gi.test(comment)) {
-    return CommentType.PASS;
-  }
-  else if (/^fail\s+[0-9]+$/gi.test(comment)) {
-    return CommentType.FAIL;
-  }
-  else if (/^ok$/gi.test(comment)) {
-    return CommentType.OK;
-  }
-  else {
-    return CommentType.OTHER;
-  }
-};
-
-function output(str) {
-  out.push(str);
-}
-
-/* Parser */
-
-var timer   = hirestime();
-var errors  = [];
-
-tap.on('comment', function(comment) {
-  var commentType = getCommentType(comment);
-  if ( commentType === CommentType.TESTS
-    || commentType === CommentType.OK
-    || commentType === CommentType.PASS
-    || commentType === CommentType.FAIL )
-  {
-    return;
-  }
-
-  output('\n  ' + chalk.white.bold(comment) + '\n');
-});
-
-tap.on('assert', function(res) {
-  if (res.ok) {
-    output('    ' + chalk.green.bold('✓') + ' ' + chalk.gray(res.name) + '\n');
-  } else {
-    assert = chalk.red.bold('⨯ ' + res.name + '\n');
-    errors.push(chalk.white(assert));
-    output('    ' + errors[errors.length-1]);
-  }
-});
-
-tap.on('extra', function(res) {
-  if (res !== '') {
-    if (res.indexOf('---') === 0){
-      errors.push(chalk.gray(res));
-      output(errors[errors.length-1]);
-      output('\n');
-    } else {
-      output('    ' + chalk.blue(res));
-      output('\n');
-    }
-  }
-});
-
-tap.on('results', function(res) {
-  var count = res.asserts.length;
-  var time  = prettyms(timer());
-  output('\n');
-
-  if (errors.length) {
-    output(chalk.red.bold(errors.length + ' failing\n'));
-  }
-  output(chalk.green.bold(Math.max(0,count-errors.length) + ' passing') + chalk.gray(' (' + time + ')'));
-
-  output('\n\n');
-});
-
-tap.on('diag', function (diag) {
-  var expected, actual, at,
-    gotExpected = true,
-    gotActual = true,
-    gotAt = true,
-    str = '';
-
-  if (diag.hasOwnProperty('expected')) {
-    expected = diag.expected;
-  } else if (diag.hasOwnProperty('wanted')) {
-    expected = diag.wanted;
-  } else {
-    gotExpected = false;
-  }
-
-  if (diag.hasOwnProperty('actual')) {
-    actual = diag.actual;
-  } else if (diag.hasOwnProperty('found')) {
-    actual = diag.found;
-  } else {
-    gotActual = false;
-  }
+var formatter = require('..')(getOptionsWithotDashes(options));
 
-  if (diag.hasOwnProperty('at')) {
-    at = diag.at;
-  }
-  else {
-    gotAt = false;
-  }
-
-  if (gotActual && gotExpected) {
-    if (typeof expected !== typeof actual ||
-        typeof expected === 'object' && (!actual || !expected)) {
-      str = 'Expected ' + typeof expected + ' but got ' + typeof actual;
-    } else if (typeof expected === 'string') {
-      if (str.indexOf('\n') >= 0) {
-        str = ansidiff.lines(expected, actual);
-      } else {
-        str = ansidiff.chars(expected, actual);
-      }
-    } else if (typeof expected === 'object') {
-      str = objdiff(expected, actual);
-    } else {
-      str = chalk.white('Expected ') + chalk.bold(''+expected) + chalk.white(' but got ') + chalk.bold(''+actual);
-    }
-  }
-
-  if (gotAt) {
-    str = str + '\n\n' + chalk.grey('At: ' + at);
-  }
-
-  if (str) {
-    str = '\n' + str;
-    str = str.replace(/\n/g, '\n      ');
-    errors[errors.length-1] += str;
-    output(str);
-    output('\n');
-  }
-
-});
-
-/* Output */
-
-process.stdin.pipe(dup).pipe(process.stdout);
+process.stdin.pipe(formatter).pipe(process.stdout);
 process.on('exit', function () {
-  process.exit(errors.length);
+  process.exit(formatter._errors.length);
 });
-
-// vim:filetype=javascript
diff --git a/index.js b/index.js
new file mode 100644
index 0000000..820755c
--- /dev/null
+++ b/index.js
@@ -0,0 +1,197 @@
+var parser    = require('tap-parser-yaml');
+var through   = require('through2');
+var duplexer  = require('duplexer');
+var hirestime = require('hirestime');
+var prettyms  = require('pretty-ms');
+var chalk     = require('chalk');
+var objdiff   = require('difflet')({
+  indent: 2,
+  comment: true
+}).compare;
+var ansidiff  = require('ansidiff');
+
+
+module.exports = function (options) {
+  if (!options) options = {};
+
+  var tap = parser();
+  var out = through();
+  var dup = duplexer(tap, out);
+
+  if (options.pessimistic) {
+    var anAssertFailed = true;
+    var originalOut = out;
+    var buffer = null;
+    tap.on('comment', function (comment) {
+      if (buffer && anAssertFailed) {
+        for (var bi = 0; bi < buffer.length; ++bi) {
+          originalOut.push(buffer[bi]);
+        }
+      }
+
+      buffer = null;
+      anAssertFailed = false;
+      out = originalOut;
+
+      if (getCommentType(comment) === CommentType.OTHER) {
+        buffer = [];
+        out = buffer;
+      }
+    });
+
+    tap.on('assert', function (res) {
+      if (!res.ok) {
+        anAssertFailed = true;
+      }
+    });
+  }
+
+  /* Helpers */
+  var CommentType = {
+    OTHER: 1,
+    TESTS: 2,
+    PASS: 3,
+    FAIL: 4,
+    OK: 5
+  };
+
+  function getCommentType(comment) {
+    if (/^tests\s+[0-9]+$/gi.test(comment)) {
+      return CommentType.TESTS;
+    }
+    else if (/^pass\s+[0-9]+$/gi.test(comment)) {
+      return CommentType.PASS;
+    }
+    else if (/^fail\s+[0-9]+$/gi.test(comment)) {
+      return CommentType.FAIL;
+    }
+    else if (/^ok$/gi.test(comment)) {
+      return CommentType.OK;
+    }
+    else {
+      return CommentType.OTHER;
+    }
+  };
+
+  function output(str) {
+    out.push(str);
+  }
+
+  /* Parser */
+
+  var timer = hirestime();
+  var errors = [];
+
+  tap.on('comment', function (comment) {
+    var commentType = getCommentType(comment);
+    if (commentType === CommentType.TESTS
+      || commentType === CommentType.OK
+      || commentType === CommentType.PASS
+      || commentType === CommentType.FAIL) {
+      return;
+    }
+
+    output('\n  ' + chalk.white.bold(comment) + '\n');
+  });
+
+  tap.on('assert', function (res) {
+    if (res.ok) {
+      output('    ' + chalk.green.bold('✓') + ' ' + chalk.gray(res.name) + '\n');
+    } else {
+      assert = chalk.red.bold('⨯ ' + res.name + '\n');
+      errors.push(chalk.white(assert));
+      output('    ' + errors[errors.length - 1]);
+    }
+  });
+
+  tap.on('extra', function (res) {
+    if (res !== '') {
+      if (res.indexOf('---') === 0) {
+        errors.push(chalk.gray(res));
+        output(errors[errors.length - 1]);
+        output('\n');
+      } else {
+        output('    ' + chalk.blue(res));
+        output('\n');
+      }
+    }
+  });
+
+  tap.on('results', function (res) {
+    var count = res.asserts.length;
+    var time = prettyms(timer());
+    output('\n');
+
+    if (errors.length) {
+      output(chalk.red.bold(errors.length + ' failing\n'));
+    }
+    output(chalk.green.bold(Math.max(0, count - errors.length) + ' passing') + chalk.gray(' (' + time + ')'));
+
+    output('\n\n');
+  });
+
+  tap.on('diag', function (diag) {
+    var expected, actual, at,
+      gotExpected = true,
+      gotActual = true,
+      gotAt = true,
+      str = '';
+
+    if (diag.hasOwnProperty('expected')) {
+      expected = diag.expected;
+    } else if (diag.hasOwnProperty('wanted')) {
+      expected = diag.wanted;
+    } else {
+      gotExpected = false;
+    }
+
+    if (diag.hasOwnProperty('actual')) {
+      actual = diag.actual;
+    } else if (diag.hasOwnProperty('found')) {
+      actual = diag.found;
+    } else {
+      gotActual = false;
+    }
+
+    if (diag.hasOwnProperty('at')) {
+      at = diag.at;
+    }
+    else {
+      gotAt = false;
+    }
+
+    if (gotActual && gotExpected) {
+      if (typeof expected !== typeof actual ||
+        typeof expected === 'object' && (!actual || !expected)) {
+        str = 'Expected ' + typeof expected + ' but got ' + typeof actual;
+      } else if (typeof expected === 'string') {
+        if (str.indexOf('\n') >= 0) {
+          str = ansidiff.lines(expected, actual);
+        } else {
+          str = ansidiff.chars(expected, actual);
+        }
+      } else if (typeof expected === 'object') {
+        str = objdiff(expected, actual);
+      } else {
+        str = chalk.white('Expected ') + chalk.bold('' + expected) + chalk.white(' but got ') + chalk.bold('' + actual);
+      }
+    }
+
+    if (gotAt) {
+      str = str + '\n\n' + chalk.grey('At: ' + at);
+    }
+
+    if (str) {
+      str = '\n' + str;
+      str = str.replace(/\n/g, '\n      ');
+      errors[errors.length - 1] += str;
+      output(str);
+      output('\n');
+    }
+
+  });
+
+  dup._errors = errors;
+
+  return dup;
+};