JavaScriptのすぐ使える7つのユーティリティ関数 ref: http://qiita.com/ka215/items/d059a78e29adef3978b5

file0.js

/**
 * Return as an object by parsing the query string of the current URL
 */
$.QueryString = (function(queries) {
  if ('' === queries) { return {}; }
  var results = {};
  for (var i=0; i<queries.length; ++i) {
    var param = queries[i].split('=');
    if (param.length !== 2) { continue; }
    results[param[0]] = decodeURIComponent(param[1].replace(/\+/g, ' '));
  }
  return results;
})(window.location.search.substr(1).split('&'));

file1.js

/**
 * Convert unit from em to pixels
 *
 * @param int em [optional]
 */
$.em2pxl = function(em) {
  if (em === undefined) { em = 1; }
  var div = $('<div style="width:'+em+'em;"></div>').appendTo('body');
  var pixel = div.width();
  div.remove();
  return pixel;
};

file10.js

var str = '三国志の人物・彭𣴎の「𣴎」の字は4バイト文字だ';
console.info([ str.substr(0, 9), $.mb_substr(str, 0, 9) ]);
//=> [ '三国志の人物・彭�', '三国志の人物・彭𣴎' ]

file11.js

/**
 * Strip tags from specified strings
 */
$.strip_tags = function( str, allowed ) {
  allowed = ( ( ( allowed || '' ) + '' ).toLowerCase().match(/<[a-z][a-z0-9]*>/g) || []).join('');
  var tags = /<\/?([a-z][a-z0-9]*)\b[^>]*>/gi, commentsAndPhpTags = /<!--[\s\S]*?-->|<\?(?:php)?[\s\S]*?\?>/gi;
  return str.replace( commentsAndPhpTags, '' ).replace( tags, function ($0, $1) {
    return allowed.indexOf('<' + $1.toLowerCase() + '>') > -1 ? $0 : '';
  });
};

file12.js

var mixedStr = '<address><strong>Full Name</strong><br><a href="mailto:#">first.last@example.com</a></address>';
console.info( $.strip_tags(mixedStr) );
//=> Full Namefirst.last@example.com

console.info( $.strip_tags(mixedStr, '<a><br>') );
//=> Full Name<br><a href="mailto:#">first.last@example.com</a>

file2.js

/**
 * Survey the width of strings
 *
 * @param string str
 * @param bool stripTags [optional]
 */
$.strWidth = function(str) {
  if ('' === arguments[0]) { return 0; }
  var ruler = $('<span style="visibility:hidden;position:absolute;white-space:nowrap;"></span>').appendTo('body');
  var width;
  if (arguments[1] !== undefined && arguments[1]) {
    str = $('<div/>').html(str).text();
  }
  width = ruler.text(str).get(0).offsetWidth;
  ruler.remove();
  return width;
};

file3.js

// 等幅フォント
$('body').css({ fontFamily: 'monospace' });
console.info([ $.strWidth('abc'), $.strWidth('ａｂｃ'), $.strWidth('ABC'), $.strWidth('ＡＢＣ') ]);
//=> [ 20, 39, 20, 39 ]

// 可変幅フォント
$('body').css({ fontFamily: 'sans-serif' });
console.info([ $.strWidth('abc'), $.strWidth('ａｂｃ'), $.strWidth('ABC'), $.strWidth('ＡＢＣ') ]);
//=> [ 24, 28, 31, 36 ]

file4.js

/**
 * Survey the size of image
 *
 * @param string src [optional]
 */
$.imageSize = function(src) {
  var imgSize = { w: 0, h: 0 };
  var img = new Image();
  img.src = src;
  imgSize.w = img.width;
  imgSize.h = img.height;
  return imgSize;
};

file5.js

var imgSize = $.imageSize( $('img').attr('src') );
$('img').attr( 'width', imgSize.w/2 ).attr( 'height', imgSize.h/2 );

file6.js

/**
 * Perform mutual conversion between the actual strings and the html entity
 * 
 * @param string str [required]
 * @param string proc [optional] "decode" (is default) or "encode"
 */
$.htmlEntities = function(str, proc) {
  if ( 'encode' === proc ) {
    var buffer = [];
    for ( var i=str.length-1; i>=0; i-- ) {
      buffer.unshift( ['&#', str[i].charCodeAt(), ';'].join('') );
    }
    return buffer.join('');
  } else {
    return str.replace( /&#(\d+);/g, function( match, dec ) {
      return String.fromCharCode( dec );
    });
  }
};

file7.js

console.info( $.htmlEntities( '<em>強調文字</em>', 'encode' ) );
//=> &#60;&#101;&#109;&#62;&#24375;&#35519;&#25991;&#23383;&#60;&#47;&#101;&#109;&#62;

console.info( $.htmlEntities('&#60;&#101;&#109;&#62;&#24375;&#35519;&#25991;&#23383;&#60;&#47;&#101;&#109;&#62;') );
//=> <em>強調文字</em>

file8.js

/**
 * Functions supported multibyte string
 */
$.isSurrogatePear = function( upper, lower ) {
  return 0xD800 <= upper && upper <= 0xDBFF && 0xDC00 <= lower && lower <= 0xDFFF;
};
$.mb_strlen = function( str ) {
  var ret = 0;
  for (var i = 0; i < str.length; i++,ret++) {
    var upper = str.charCodeAt(i);
    var lower = str.length > (i + 1) ? str.charCodeAt(i + 1) : 0;
    if ( $.isSurrogatePear( upper, lower ) ) { i++; }
  }
  return ret;
};
$.mb_substr = function( str, begin, end ) {
  var ret = '';
  for (var i = 0, len = 0; i < str.length; i++, len++) {
    var upper = str.charCodeAt(i);
    var lower = str.length > (i + 1) ? str.charCodeAt(i + 1) : 0;
    var s = '';
    if( $.isSurrogatePear( upper, lower ) ) {
      i++;
      s = String.fromCharCode( upper, lower );
    } else {
      s = String.fromCharCode( upper );
    }
    if ( begin <= len && len < end ) { ret += s; }
  }
  return ret;
};

file9.js

var str = '三国志の人物・彭𣴎の「𣴎」の字は4バイト文字だ'; //:23文字
console.info([ str.length, $.mb_strlen(str) ]);
//=> [ 25, 23 ]