Сергей Соколов

var mdk_win = window.open('https://vk.com/mudakoff', 'mdk_win', 'width=600,height=400');
mdk_win.addEventListener('load', function(){
  console.log('окно MDK загружено');
});

arr2 = arr2.filter(e => !~arr.indexOf(e));
// facebook.com,ya.ru

function test(varbl) {
  varbl = varbl || 0;
  alert(varbl);
}

test();
test( 100500);

1. объявить эту переменную: var varbl;
   
2. дать или не дать ей какое-то значение: if( Math.random() > 0.5) varbl = 100500;
   

Calc = function(){
  this.sum = function(){
    return Array
      .prototype
      .slice
      .call(arguments)
      .reduce(function(p,c){return +p+c}, 0)
  }
}

let c = new Calc;
c.sum(2,4,6) // 12

00 01 02
10 11 12
20 21 22

00        :  0+0 = 0
10, 01    :  1+0 = 0+1 = 1
20, 11, 02:  2+0 = 1+1 = 0+2 = 2

var arr = [
  'o,x,x'.split(','),
  'x,o,o'.split(','),
  'o,x,o'.split(','),
];

var r, c, key, diags = {};
for(r = 0; r < arr.length; r++) {
  for(c = 0; c < arr[r].length; c++) {
    key = r + arr[r].length - 1 - c; // слева сверху вправо вниз
    // key = r + c; // слева снизу вправо вверх
    
    if( diags.hasOwnProperty(key)) {
      if( diags[key] !== arr[r][c]) diags[key] = false;
    } else {
      diags[key] = arr[r][c];
    }
  }
}

for( key in diags) if( diags[key] === false) delete diags[key];
// {"0":"x","2":"o","3":"x","4":"o"}

function user_params(id, param, callback) {
  vk('users.get', {user_ids: id, fields: param}, function(error, response){
    if (error) {
      console.log(error);
    } else callback(response[0][param]);
  });
};

function roundTS(ts) {
  var D = new Date(ts);
  var m = 15 + Math.ceil( D.getMinutes() / 15);
  D.setMinutes(m);
  return D.getTime();
}

function roundMinArr( D, arr) {
  var i, m = D.getMinutes();  
  arr.sort((a,b)=>a-b);
  for(i in arr) {
    if( arr[i] < m) continue;
    D.setMinutes(arr[i]);
    return D;
  }
  D.setMinutes(60 + arr[0]);
  return D;
}

var D = roundMinArr( new Date('2017-08-16T12:17+03:00'), [0,15,35,44,59]);
D.toString() // Wed Aug 16 2017 12:35:00 GMT+0300 (MSK)

function getById( obj, id) {
  var i, found;
  if( obj.id === id) return obj;
  if( obj.hasOwnProperty('childGroups')) {
    for( i in obj.childGroups) {
      if( found = getById( obj.childGroups[i], id)) return found;
    }
  }
  return;
}

getById( obj,3) // {"id":3,"parentId":1,"childGroups":[{"id":6,"parentId":3},{"id":7,"parentId":3}]}

function countSymbols(s) {
  return s.split('').reduce(
    (p,c) => (p.hasOwnProperty(c)?p[c]++:p[c]=1, p), {}
  );
}
var r = countSymbols('hello'); // {"h":1,"e":1,"l":2,"o":1}

function bad( obj, name) {
  return eval('obj.' + name);     
}
bad(r, 'foo.bar'); // 'value'

function better( obj, name) {
  var parts = name.split('.'), i, cursor = r;
  
  for( i = 0; i < parts.length; i++) {
    if( !cursor.hasOwnProperty( parts[i])) throw('No such property: ' + parts[i]);
    cursor = cursor[parts[i]];
  }
  
  return cursor;
}

better(r, 'foo.bar'); // 'value'

<div class="textfield" contentEditable="true">напиши-ка!
</div>

.textfield {
	font-size:16px;
	color:white;
	min-height:16px;
	line-height:20px;
	width:200px;
	border:1px solid #999;
	background:  url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAIAAAAC64paAAAAGXRFWHRTb2Z0d2FyZQBBZG9iZSBJbWFnZVJlYWR5ccllPAAAACtJREFUeNpiNDY2ZiAXMDFQAEY1j2oe1TyoNLNoOu0nX/P1fY4D42yAAAMA7aYDxR1GwC8AAAAASUVORK5CYII=')
}
body {background:#333; font-family:Arial, sans-serif}

<textarea rows="1" cols="20" id="ta1" class="textfield">напиши-ка!
</textarea>

var ta1 = document.getElementById('ta1');
ta1.addEventListener('input', function(){
	var rows = Math.ceil( ta1.scrollHeight / 20 ) - 1;
	ta1.style.height = 20 * rows + 'px';
});

closest: function( selectors, context ) {
		var cur,
			i = 0,
			l = this.length,
			matched = [],
			targets = typeof selectors !== "string" && jQuery( selectors );

		// Positional selectors never match, since there's no _selection_ context
		if ( !rneedsContext.test( selectors ) ) {
			for ( ; i < l; i++ ) {
				for ( cur = this[ i ]; cur && cur !== context; cur = cur.parentNode ) {

					// Always skip document fragments
					if ( cur.nodeType < 11 && ( targets ?
						targets.index( cur ) > -1 :

						// Don't pass non-elements to Sizzle
						cur.nodeType === 1 &&
							jQuery.find.matchesSelector( cur, selectors ) ) ) {

						matched.push( cur );
						break;
					}
				}
			}
		}

		return this.pushStack( matched.length > 1 ? jQuery.uniqueSort( matched ) : matched );
	},

$('#catalog>li>a').each(function(){
  $(this).html( function(i,t){
    return t.replace(/(\(\d+\))/, '<span>$1</span>')
  });
});