prototype/src/string.js

String.interpret = function(value){
  return value == null ? '' : String(value);
}

Object.extend(String.prototype, {
  gsub: function(pattern, replacement) {
    var result = '', source = this, match;
    replacement = arguments.callee.prepareReplacement(replacement);
    
    while (source.length > 0) {
      if (match = source.match(pattern)) {
        result += source.slice(0, match.index);
        result += String.interpret(replacement(match));
        source  = source.slice(match.index + match[0].length);
      } else {
        result += source, source = '';
      }
    }
    return result;
  },
  
  sub: function(pattern, replacement, count) {
    replacement = this.gsub.prepareReplacement(replacement);
    count = count === undefined ? 1 : count;
    
    return this.gsub(pattern, function(match) {
      if (--count < 0) return match[0];
      return replacement(match);
    });
  },
  
  scan: function(pattern, iterator) {
    this.gsub(pattern, iterator);
    return this;
  },
  
  truncate: function(length, truncation) {
    length = length || 30;
    truncation = truncation === undefined ? '...' : truncation;
    return this.length > length ? 
      this.slice(0, length - truncation.length) + truncation : this;
  },

  strip: function() {
    return this.replace(/^\s+/, '').replace(/\s+$/, '');
  },
  
  stripTags: function() {
    return this.replace(/<\/?[^>]+>/gi, '');
  },

  stripScripts: function() {
    return this.replace(new RegExp(Prototype.ScriptFragment, 'img'), '');
  },
  
  extractScripts: function() {
    var matchAll = new RegExp(Prototype.ScriptFragment, 'img');
    var matchOne = new RegExp(Prototype.ScriptFragment, 'im');
    return (this.match(matchAll) || []).map(function(scriptTag) {
      return (scriptTag.match(matchOne) || ['', ''])[1];
    });
  },
  
  evalScripts: function() {
    return this.extractScripts().map(function(script) { return eval(script) });
  },

  escapeHTML: function() {
    var div = document.createElement('div');
    var text = document.createTextNode(this);
    div.appendChild(text);
    return div.innerHTML;
  },

  unescapeHTML: function() {
    var div = document.createElement('div');
    div.innerHTML = this.stripTags();
    return div.childNodes[0] ? (div.childNodes.length > 1 ? 
      $A(div.childNodes).inject('',function(memo,node){ return memo+node.nodeValue }) : 
      div.childNodes[0].nodeValue) : '';
  },
  
  toQueryParams: function(separator) {
    var match = this.strip().match(/([^?#]*)(#.*)?$/);
    if (!match) return {};
    
    return match[1].split(separator || '&').inject({}, function(hash, pair) {
      if ((pair = pair.split('='))[0]) {
        var name = decodeURIComponent(pair[0]);
        var value = pair[1] ? decodeURIComponent(pair[1]) : undefined;

        if (hash[name] !== undefined) {
          if (hash[name].constructor != Array)
            hash[name] = [hash[name]];
          if (value) hash[name].push(value);
        }
        else hash[name] = value;
      }
      return hash;
    });
  },
  
  toArray: function() {
    return this.split('');
  },

  succ: function() {
    return this.slice(0, this.length - 1) +
      String.fromCharCode(this.charCodeAt(this.length - 1) + 1);
  },

  camelize: function() {
    var parts = this.split('-'), len = parts.length;
    if (len == 1) return parts[0];
    
    var camelized = this.charAt(0) == '-' 
      ? parts[0].charAt(0).toUpperCase() + parts[0].substring(1)
      : parts[0];
    
    for (var i = 1; i < len; i++)
      camelized += parts[i].charAt(0).toUpperCase() + parts[i].substring(1);
   
    return camelized;
  },
  
  capitalize: function(){
    return this.charAt(0).toUpperCase() + this.substring(1).toLowerCase();
  },
  
  underscore: function() {
    return this.gsub(/::/, '/').gsub(/([A-Z]+)([A-Z][a-z])/,'#{1}_#{2}').gsub(/([a-z\d])([A-Z])/,'#{1}_#{2}').gsub(/-/,'_').toLowerCase();
  },

  dasherize: function() {
    return this.gsub(/_/,'-');
  },

  inspect: function(useDoubleQuotes) {
    var escapedString = this.replace(/\\/g, '\\\\');
    if (useDoubleQuotes)
      return '"' + escapedString.replace(/"/g, '\\"') + '"';
    else
      return "'" + escapedString.replace(/'/g, '\\\'') + "'";
  }
});

String.prototype.gsub.prepareReplacement = function(replacement) {
  if (typeof replacement == 'function') return replacement;
  var template = new Template(replacement);
  return function(match) { return template.evaluate(match) };
}

String.prototype.parseQuery = String.prototype.toQueryParams;

var Template = Class.create();
Template.Pattern = /(^|.|\r|\n)(#\{(.*?)\})/;
Template.prototype = {
  initialize: function(template, pattern) {
    this.template = template.toString();
    this.pattern  = pattern || Template.Pattern;
  },
  
  evaluate: function(object) {
    return this.template.gsub(this.pattern, function(match) {
      var before = match[1];
      if (before == '\\') return match[2];
      return before + String.interpret(object[match[3]]);
    });
  }
}