add exclude option to restrict passwords (#15)

This commit adds an option, `exclude`, through which one can pass a
string of characters that will be removed from the password generation
pool.

For example, to remove some similar characters (without
excludeSimilarCharacters), you can now pass { exclude: 'ilLI|' }.

README.md

@@ -55,4 +55,5 @@ Any of these can be passed into the options object for each function.
 | symbols                  | Boolean, put symbols in password.                   |     false     |
 | uppercase                | Boolean, use uppercase letters in password.         |      true     |
 | excludeSimilarCharacters | Boolean, exclude similar chars, like 'i' and 'l'.   |     false     |
+| exclude                  | String, characters to be excluded from password.    |       ''      |
 | strict                   | Boolean, password must include at least one character from each pool. |     false     |

src/generate.js

@@ -58,6 +58,7 @@ self.generate = function(options) {
 	if (!options.hasOwnProperty('length')) options.length = 10;
 	if (!options.hasOwnProperty('numbers')) options.numbers = false;
 	if (!options.hasOwnProperty('symbols')) options.symbols = false;
+	if (!options.hasOwnProperty('exclude')) options.exclude = '';
 	if (!options.hasOwnProperty('uppercase')) options.uppercase = true;
 	if (!options.hasOwnProperty('excludeSimilarCharacters')) options.excludeSimilarCharacters = false;
 	if (!options.hasOwnProperty('strict')) options.strict = false;
@@ -84,11 +85,18 @@ self.generate = function(options) {
 	if (options.symbols) {
 		pool += symbols;
 	}
+
 	// similar characters
 	if (options.excludeSimilarCharacters) {
 		pool = pool.replace(similarCharacters, '');
 	}
 
+	// excludes characters from the pool
+	var i = options.exclude.length;
+	while (i--) {
+		pool = pool.replace(options.exclude[i], '');
+	}
+
 	var password = generate(options, pool);
 
 	return password;

test/generator.js

@@ -77,6 +77,16 @@ describe('generate-password', function() {
 				assert.equal(passwords.length, amountToGenerate);
 			});
 
+			it('should generate strict random sequence that avoids all excluded characters', function() {
+				var passwords = generator.generateMultiple(amountToGenerate, {length: 4, strict: true, symbols: true, exclude: 'abcdefg+_-=}{[]|:;"/?.><,`~'});
+
+				passwords.forEach(function(password) {
+					assert.match(password, /[!@#$%^&*()]/, 'password uses normal symbols');
+					assert.notMatch(password, /[abcdefg+_\-=}{[\]|:;"/?.><,`~]/, 'password avoids excluded characters from the full pool');
+				});
+				assert.equal(passwords.length, amountToGenerate);
+			});
+
 			it('should throw an error if rules don\'t correlate with length', function() {
 				assert.throws(function() {
 					generator.generate({length: 2, strict: true, symbols: true, numbers: true});