diff --git a/underscore.string/underscore.string-tests.ts b/underscore.string/underscore.string-tests.ts
new file mode 100644
index 000000000..cfbf3bc2d
--- /dev/null
+++ b/underscore.string/underscore.string-tests.ts
@@ -0,0 +1,131 @@
+/// <reference path='../underscore/underscore.d.ts' />
+/// <reference path='underscore.string.d.ts' />
+
+_ = _.string;
+
+_.numberFormat(1000, 2);
+_.numberFormat(123456789.123, 5, '.', ',');
+
+_.levenshtein('kitten', 'kittah');
+
+_.capitalize('foo Bar');
+
+_.chop('whitespace', 3);
+
+_.clean(' foo    bar   ');
+
+_.chars('Hello');
+
+_.swapCase('hELLO');
+
+_.str.include('foobar', 'ob');
+
+_.count('Hello world', 'l');
+
+_.escapeHTML('<div>Blah blah blah</div>');
+
+_.unescapeHTML('&lt;div&gt;Blah blah blah&lt;/div&gt;');
+
+_.insert('Hello ', 6, 'world');
+
+_.isBlank('');
+_.isBlank('\n');
+_.isBlank(' ');
+_.isBlank('a');
+
+_.join(' ', 'foo', 'bar');
+
+_.lines('Hello\nWorld');
+
+_.str.reverse('foobar');
+
+_.splice('https://edtsech@bitbucket.org/edtsech/underscore.strings', 30, 7, 'epeli');
+
+_.startsWith('image.gif', 'image');
+
+_.endsWith('image.gif', 'gif');
+
+_.succ('a');
+_.succ('A');
+
+_.titleize('my name is epeli');
+
+_.camelize('-moz-transform');
+
+_.classify('some_class_name');
+
+_.underscored('MozTransform');
+
+_.dasherize('MozTransform');
+
+_.humanize('  capitalize dash-CamelCase_underscore trim  ');
+
+_.trim('  foobar   ');
+_.trim('_-foobar-_', '_-');
+
+_.truncate('Hello world', 5);
+_.truncate('Hello', 10);
+
+_.prune('Hello, world', 5);
+_.prune('Hello, world', 8);
+_.prune('Hello, world', 5, ' (read a lot more)');
+_.prune('Hello, cruel world', 15);
+_.prune('Hello', 10);
+
+_.words('   I   love   you   ');
+_.words('I_love_you', '_');
+_.words('I-love-you', /-/);
+_.words('   ');
+
+_.sprintf('%.1f', 1.17);
+
+_.pad('1', 8);
+_.pad('1', 8, '0');
+_.pad('1', 8, '0', 'right');
+_.pad('1', 8, '0', 'both');
+_.pad('1', 8, 'bleepblorp', 'both');
+
+_.lpad('1', 8, '0');
+
+_.rpad('1', 8, '0');
+
+_.toNumber('2.556');
+_.toNumber('2.556', 1);
+
+_.strRight('This_is_a_test_string', '_');
+
+_.strRightBack('This_is_a_test_string', '_');
+
+_.strLeft('This_is_a_test_string', '_');
+
+_.strLeftBack('This_is_a_test_string', '_');
+
+_.stripTags('a <a href="#">link</a>');
+_.stripTags('a <a href="#">link</a><script>alert("hello world!")</script>');
+
+_.toSentence(['jQuery', 'Mootools', 'Prototype']);
+_.toSentence(['jQuery', 'Mootools', 'Prototype'], ', ', ' unt ');
+
+_.toSentenceSerial(['jQuery', 'Mootools']);
+_.toSentenceSerial(['jQuery', 'Mootools', 'Prototype']);
+_.toSentenceSerial(['jQuery', 'Mootools', 'Prototype'], ', ', ' unt ');
+
+_.repeat('foo', 3);
+_.repeat('foo', 3, 'bar');
+
+_.surround('foo', 'ab');
+
+_.quote('foo');
+
+_.unquote('"foo"');
+_.unquote("'foo'", "'");
+
+_.slugify("Un éléphant à l'orée du bois");
+
+['foo20', 'foo5'].sort(_.naturalCmp);
+
+_.toBoolean('true');
+_.toBoolean('FALSE');
+_.toBoolean('random');
+_.toBoolean('truthy', ['truthy'], ['falsy']);
+_.toBoolean('true only at start', [/^true/]);
diff --git a/underscore.string/underscore.string.d.ts b/underscore.string/underscore.string.d.ts
new file mode 100644
index 000000000..7996d7cbb
--- /dev/null
+++ b/underscore.string/underscore.string.d.ts
@@ -0,0 +1,515 @@
+// Type definitions for underscore.string
+// Project: https://github.com/epeli/underscore.string
+// Definitions by: Ry Racherbaumer <http://github.com/rygine>
+// Definitions: https://github.com/borisyankov/DefinitelyTyped
+
+declare module 'underscore.string' {
+
+    /**
+     * Determine if a string is 'blank.'
+     * @param str
+     */
+    function isBlank(str: string): boolean;
+
+    /**
+     * Removes all html tags from string.
+     * @param str
+     */
+    function stripTags(str: string): string;
+
+    /**
+     * Converts first letter of the string to uppercase.
+     * ('foo Bar') => 'Foo Bar'
+     * @param str
+     */
+    function capitalize(str: string): string;
+
+    /**
+     * Chop a string into pieces.
+     * ('whitespace', 3) => ['whi','tes','pac','e']
+     * @param str String to chop
+     * @param step Size of the pieces
+     */
+    function chop(str: string, step: number): Array;
+
+    /**
+     * Compress some whitespaces to one.
+     * (' foo    bar   ') => 'foo bar'
+     * @param str
+     */
+    function clean(str: string): string;
+
+    /**
+     * Count occurences of a sub string.
+     * ('Hello world', 'l') => 3
+     * @param str
+     * @param substr
+     */
+    function count(str: string, substr: string): number;
+
+    /**
+     * Convert string to an array of characters.
+     * ('Hello') => ['H','e','l','l','o']
+     * @param str
+     */
+    function chars(str: string): Array;
+
+    /**
+     * Returns a copy of the string in which all the case-based characters have had their case swapped.
+     * ('hELLO') => 'Hello'
+     * @param str
+     */
+    function swapCase(str: string): string;
+
+    /**
+     * Converts HTML special characters to their entity equivalents.
+     * ('<div>Blah blah blah</div>') => '&lt;div&gt;Blah blah blah&lt;/div&gt;'
+     * @param str
+     */
+    function escapeHTML(str: string): string;
+
+    /**
+     * Converts entity characters to HTML equivalents.
+     * ('&lt;div&gt;Blah blah blah&lt;/div&gt;') => '<div>Blah blah blah</div>'
+     * @param str
+     */
+    function unescapeHTML(str: string): string;
+
+    /**
+     * Escape a string for use in a regular expression.
+     * @param str
+     */
+    function escapeRegExp(str: string): string;
+
+    /**
+     * Splice a string like an array.
+     * @param str
+     * @param i
+     * @param howmany
+     * @param substr
+     */
+    function splice(str: string, i: number, howmany: number, substr?: string): string;
+
+    /**
+     * Insert a string at index.
+     * @param str
+     * @param i
+     * @param substr
+     */
+    function insert(str: string, i: number, substr: string): string;
+
+    /**
+     * Tests if string contains a substring.
+     * ('foobar', 'ob') => true
+     * @param str
+     * @param needle
+     */
+    function include(str: string, needle: string): boolean;
+
+    /**
+     * Tests if string contains a substring.
+     * ('foobar', 'ob') => true
+     * @param str
+     * @param needle
+     */
+    function contains(str: string, needle: string): boolean;
+
+    /**
+     * Joins strings together with given separator.
+     * (' ', 'foo', 'bar') => 'foo bar'
+     * @param separator
+     * @param args
+     */
+    function join(separator: string, ...args: string[]): string;
+
+    /**
+     * Split string by newlines character.
+     * ('Hello\nWorld') => ['Hello', 'World']
+     * @param str
+     */
+    function lines(str: string): Array;
+
+    /**
+     * Return reversed string.
+     * ('foobar') => 'raboof'
+     * @param str
+     */
+    function reverse(str: string): string;
+
+    /**
+     * Checks if string starts with another string.
+     * ('image.gif', 'image') => true
+     * @param str
+     * @param starts
+     */
+    function startsWith(str: string, starts: string): boolean;
+
+    /**
+     * Checks if string ends with another string.
+     * ('image.gif', 'gif') => true
+     * @param value
+     * @param starts
+     */
+    function endsWith(value: string, starts: string): boolean;
+
+    /**
+     * Returns the successor to passed string.
+     * ('a') => 'b'
+     * @param str
+     */
+    function succ(str: string): string;
+
+    /**
+     * Capitalize first letter of every word in the string.
+     * ('my name is epeli') => 'My Name Is Epeli'
+     * @param str
+     */
+    function titleize(str: string): string;
+
+    /**
+     * Converts underscored or dasherized string to a camelized one.
+     * ('-moz-transform') => 'MozTransform'
+     * @param str
+     */
+    function camelize(str: string): string;
+
+    /**
+     * Converts a camelized or dasherized string into an underscored one.
+     * ('MozTransform') => 'moz_transform'
+     * @param str
+     */
+    function underscored(str: string): string;
+
+    /**
+     * Converts a underscored or camelized string into an dasherized one.
+     * ('MozTransform') => '-moz-transform'
+     * @param str
+     */
+    function dasherize(str: string): string;
+
+    /**
+     * Converts string to camelized class name.
+     * ('some_class_name') => 'SomeClassName'
+     * @param str
+     */
+    function classify(str: string): string;
+
+    /**
+     * Converts an underscored, camelized, or dasherized string into a humanized one.
+     * Also removes beginning and ending whitespace, and removes the postfix '_id'.
+     * ('  capitalize dash-CamelCase_underscore trim  ') => 'Capitalize dash camel case underscore trim'
+     * @param str
+     */
+    function humanize(str: string): string;
+
+    /**
+     * Trims defined characters from begining and ending of the string.
+     * Defaults to whitespace characters.
+     * ('  foobar   ') => 'foobar'
+     * ('_-foobar-_', '_-') => 'foobar'
+     * @param str
+     * @param characters
+     */
+    function trim(str: string, characters?: string): string;
+
+    /**
+     * Trims defined characters from begining and ending of the string.
+     * Defaults to whitespace characters.
+     * ('  foobar   ') => 'foobar'
+     * ('_-foobar-_', '_-') => 'foobar'
+     * @param str
+     * @param characters
+     */
+    function strip(str: string, characters?: string): string;
+
+    /**
+     * Left trim. Similar to trim, but only for left side.
+     * @param str
+     * @param characters
+     */
+    function ltrim(str: string, characters?: string): string;
+
+    /**
+     * Left trim. Similar to trim, but only for left side.
+     * @param str
+     * @param characters
+     */
+    function lstrip(str: string, characters?: string): string;
+
+    /**
+     * Right trim. Similar to trim, but only for right side.
+     * @param str
+     * @param characters
+     */
+    function rtrim(str: string, characters?: string): string;
+
+    /**
+     * Right trim. Similar to trim, but only for right side.
+     * @param str
+     * @param characters
+     */
+    function rstrip(str: string, characters?: string): string;
+
+    /**
+     * Truncate string to specified length.
+     * ('Hello world').truncate(5) => 'Hello...'
+     * ('Hello').truncate(10) => 'Hello'
+     * @param str
+     * @param length
+     * @param truncateStr
+     */
+    function truncate(str: string, length: number, truncateStr?: string): string;
+
+    /**
+     * Elegant version of truncate.
+     * Makes sure the pruned string does not exceed the original length.
+     * Avoid half-chopped words when truncating.
+     * ('Hello, cruel world', 15) => 'Hello, cruel...'
+     * @param str
+     * @param length
+     * @param pruneStr
+     */
+    function prune(str: string, length: number, pruneStr?: string): string;
+
+    /**
+     * Split string by delimiter (String or RegExp).
+     * /\s+/ by default.
+     * ('   I   love   you   ') => ['I','love','you']
+     * ('I_love_you', '_') => ['I','love','you']
+     * @param str
+     * @param delimiter
+     */
+    function words(str: string, delimiter?: string): Array;
+
+    /**
+     * Pads a string with characters until the total string length is equal to the passed length parameter.
+     * By default, pads on the left with the space char (' ').
+     * padStr is truncated to a single character if necessary.
+     * ('1', 8) => '       1'
+     * ('1', 8, '0') => '00000001'
+     * ('1', 8, '0', 'right') => '10000000'
+     * ('1', 8, '0', 'both') => '00001000'
+     * ('1', 8, 'bleepblorp', 'both') => 'bbbb1bbb'
+     * @param str
+     * @param length
+     * @param padStr
+     * @param type
+     */
+    function pad(str: string, length: number, padStr?:string, type?: string): string;
+
+    /**
+     * Left-pad a string.
+     * Alias for pad(str, length, padStr, 'left')
+     * ('1', 8, '0') => '00000001'
+     * @param str
+     * @param length
+     * @param padStr
+     */
+    function lpad(str: string, length: number, padStr?: string): string;
+
+    /**
+     * Left-pad a string.
+     * Alias for pad(str, length, padStr, 'left')
+     * ('1', 8, '0') => '00000001'
+     * @param str
+     * @param length
+     * @param padStr
+     */
+    function rjust(str: string, length: number, padStr?: string): string;
+
+    /**
+     * Right-pad a string.
+     * Alias for pad(str, length, padStr, 'right')
+     * ('1', 8, '0') => '10000000'
+     * @param str
+     * @param length
+     * @param padStr
+     */
+    function rpad(str: string, length: number, padStr?: string): string;
+
+    /**
+     * Right-pad a string.
+     * Alias for pad(str, length, padStr, 'right')
+     * ('1', 8, '0') => '10000000'
+     * @param str
+     * @param length
+     * @param padStr
+     */
+    function ljust(str: string, length: number, padStr?: string): string;
+
+    /**
+     * Left/right-pad a string.
+     * Alias for pad(str, length, padStr, 'both')
+     * ('1', 8, '0') => '00001000'
+     * @param str
+     * @param length
+     * @param padStr
+     */
+    function lrpad(str: string, length: number, padStr?: string): string;
+
+    /**
+     * Left/right-pad a string.
+     * Alias for pad(str, length, padStr, 'both')
+     * ('1', 8, '0') => '00001000'
+     * @param str
+     * @param length
+     * @param padStr
+     */
+    function center(str: string, length: number, padStr?: string): string;
+
+    function sprintf(format: string, ...args: any[]): string;
+
+    function vsprintf(fmt: string, ...argv: any[]): string;
+
+    /**
+     * Parse string to number.
+     * Returns NaN if string can't be parsed to number.
+     * ('2.556').toNumber() => 3
+     * ('2.556').toNumber(1) => 2.6
+     * @param str
+     * @param decimals
+     */
+    function toNumber(str: string, decimals?: number): number;
+
+    function numberFormat(number: number, dec?: number, dsep?: string, tsep?: string): string;
+
+    /**
+     * Searches a string from left to right for a pattern.
+     * Returns a substring consisting of the characters in the string that are to the right of the pattern.
+     * If no match found, returns entire string.
+     * ('This_is_a_test_string').strRight('_') => 'is_a_test_string'
+     * @param str
+     * @param sep
+     */
+    function strRight(str: string, sep: string): string;
+
+    /**
+     * Searches a string from right to left for a pattern.
+     * Returns a substring consisting of the characters in the string that are to the right of the pattern.
+     * If no match found, returns entire string.
+     * ('This_is_a_test_string').strRightBack('_') => 'string'
+     * @param str
+     * @param sep
+     */
+    function strRightBack(str: string, sep: string): string;
+
+    /**
+     * Searches a string from left to right for a pattern.
+     * Returns a substring consisting of the characters in the string that are to the left of the pattern.
+     * If no match found, returns entire string.
+     * ('This_is_a_test_string').strLeft('_') => 'This'
+     * @param str
+     * @param sep
+     */
+    function strLeft(str: string, sep: string): string;
+
+    /**
+     * Searches a string from right to left for a pattern.
+     * Returns a substring consisting of the characters in the string that are to the left of the pattern.
+     * If no match found, returns entire string.
+     * ('This_is_a_test_string').strLeftBack('_') => 'This_is_a_test'
+     * @param str
+     * @param sep
+     */
+    function strLeftBack(str: string, sep: string): string;
+
+    /**
+     * Join an array into a human readable sentence.
+     * (['jQuery', 'Mootools', 'Prototype']) => 'jQuery, Mootools and Prototype'
+     * (['jQuery', 'Mootools', 'Prototype'], ', ', ' unt ') => 'jQuery, Mootools unt Prototype'
+     * @param array
+     * @param separator
+     * @param lastSeparator
+     * @param serial
+     */
+    function toSentence(array: Array, separator?: string, lastSeparator?: string, serial?: boolean): string;
+
+    /**
+     * The same as toSentence, but uses ', ' as default for lastSeparator.
+     * @param array
+     * @param separator
+     * @param lastSeparator
+     */
+    function toSentenceSerial(array: Array, separator?: string, lastSeparator?: string): string;
+
+    /**
+     * Transform text into a URL slug. Replaces whitespaces, accentuated, and special characters with a dash.
+     * ('Un éléphant à l'orée du bois') => 'un-elephant-a-loree-du-bois'
+     * @param str
+     */
+    function slugify(str: string): string;
+
+    /**
+     * Surround a string with another string.
+     * ('foo', 'ab') => 'abfooab'
+     * @param str
+     * @param wrapper
+     */
+    function surround(str: string, wrapper: string): string;
+
+    /**
+     * Quotes a string.
+     * quoteChar defaults to "
+     * ('foo') => '"foo"'
+     * @param str
+     */
+    function quote(str: string, quoteChar?: string): string;
+
+    /**
+     * Quotes a string.
+     * quoteChar defaults to "
+     * ('foo') => '"foo"'
+     * @param str
+     */
+    function q(str: string, quoteChar?: string): string;
+
+    /**
+     * Unquotes a string.
+     * quoteChar defaults to "
+     * ('"foo"') => 'foo'
+     * ("'foo'", "'") => 'foo'
+     * @param str
+     */
+    function unquote(str: string, quoteChar?: string): string;
+
+    /**
+     * Repeat a string with an optional separator.
+     * ('foo', 3) => 'foofoofoo'
+     * ('foo', 3, 'bar') => 'foobarfoobarfoo'
+     * @param value
+     * @param count
+     * @param separator
+     */
+    function repeat(value: string, count: number, separator?:string): string;
+
+    /**
+     * Naturally sort strings like humans would do.
+     * Caution: this function is charset dependent.
+     * @param str1
+     * @param str2
+     */
+    function naturalCmp(str1: string, str2: string): number;
+
+    /**
+     * Calculates Levenshtein distance between two strings.
+     * ('kitten', 'kittah') => 2
+     * @param str1
+     * @param str2
+     */
+    function levenshtein(str1: string, str2: string): number;
+
+    /**
+     * Turn strings that can be commonly considered as booleans to real booleans.
+     * Such as "true", "false", "1" and "0". This function is case insensitive.
+     * ('true') => true
+     * ('FALSE') => false
+     * ('random') => undefined
+     * ('truthy', ['truthy'], ['falsy']) => true
+     * ('true only at start', [/^true/]) => true
+     * @param str
+     * @param trueValues
+     * @param falseValues
+     */
+    function toBoolean(str: string, trueValues?: Array, falseValues?: Array): boolean;
+
+}