<ul>
 <li>list <strong>item 1</strong></li>
 <li><span>list item 2</span></li>
 <li>list item 3</li>
</ul>

$("ul").click(function(event) {
 var $target = $(event.target);
 if ( $target.is("li") ) {
  $target.css("background-color", "red");
 }
});

// 是不是一个div
elem.is('div') && console.log("it's a div");
// 是不是有包含(也可以有其他类名)bigbox的类名的元素?
elem.is('.bigbox') && console.log("it has the bigbox class!");
// 是不是隐藏的?
elem.is(':not(:visible)') && console.log("it is hidden!");

elem.animate({'width':200},1000);
// 是否正在动画
elem.is(':animated') && console.log("it is animated!");

elem.animate({'width':200},1000);
// 是否正在动画
elem.is(':animated') && console.log("it is animated!");

jQuery.fn.exists = function(){ return this.length > 0; }
console.log($('#elem').exists() ? "exists!" : "doesn't exist!");

$('li','#firstList').each(function(){
  console.log($(this).html());
});

$('<div>',{
  "class": "bigBlue",
  "css": {
    "background-color":"purple"
  },
  "width" : 20,
  "height": 20,
  "animate" : {  // 可以设置div的动画效果
    "width": 200,
    "height":50
  }
}).appendTo('#result');

<ul id="meals"> <li> <ul class="breakfast"> <li class="eggs">No</li> <li class="toast">No</li> <li class="juice">No</li> </ul> </li> </ul>

breakfast.find('.eggs').text('Yes').end() // back to breakfast
.find('.toast').text('Yes').end().find('.juice').toggleClass('juice coffee').text('Yes');

$(function(){
  $(document).on("contextmenu",function(e){
    e.preventDefault();
  });
}); 

var elem = $('#elem');
for(var i = 0; i < 100; i++){
  elem.append('<li>element '+i+'</li>');
}

var elem = $('#elem'),
arr = [];
for(var i = 0; i < 100; i++){
  arr.push('<li>element '+i+'</li>');
}
elem.append(arr.join(''));

var url = 'http://tutorialzine.com/books/jquery-trickshots?trick=12&&abc=123#comments';
  var a = $('<a>',{ href: url });
  console.log(url); 
  console.log('Host name: ' + a.prop('hostname')); //Host name: tutorialzine.com
  console.log('Path: ' + a.prop('pathname')); //Path: /books/jquery-trickshots
  console.log('Query: ' + a.prop('search')); //Query: ?trick=12&&abc=123
  console.log('Protocol: ' + a.prop('protocol')); //Protocol: http:
  console.log('Hash: ' + a.prop('hash')); //Hash: #comments

$('#pancakes li').eq(0).remove();
$('#pancakes li').eq(1).remove();
$('#pancakes li').eq(2).remove();

//第二种
var pancakes = $('#pancakes li');
pancakes.eq(0).remove();
pancakes.eq(1).remove();
pancakes.eq(2).remove();
//第三种
pancakes.eq(0).remove().end().eq(1).remove().end().eq(2).remove().end();

var press = $('#press');
press.on('click',function(e, how){
  how = how || '';
  alert('The buton was clicked ' + how + '!');
});
press.trigger('click');
press.trigger('click',['fast']);

<button id="button1">Jump</button> <button id="button2">Punch</button> <button id="button3">Click</button> <button id="clear" style="float: right;">Clear</button> <div id="eventDiv"></div>

var button1 = $('#button1'),
  button2 = $('#button2'),
  button3 = $('#button3'),
  clear = $('#clear'),
  div = $('#eventDiv');
div.on({
  jump : function(){
    alert('Jumped!');
  },
  punch : function(e,data){
    alert('Punched '+data+'!');
  },
  click : function(){
    alert('Simulated click!');
  }
});
button1.click(function(){
  div.trigger('jump');
});
button2.click(function(){
  // Pass data along with the event
  div.trigger('punch',['hard']);
});
button3.click(function(){
  div.trigger('click');
});
clear.click(function(){
  //some clear code
});

// Define some variables
var ball = $('<div id="ball"></div>').appendTo('body'),
startPosition = {}, elementPosition = {};
// Listen for mouse and touch events
ball.on('mousedown touchstart',function(e){
  e.preventDefault();
  // Normalizing the touch event object
  e = (e.originalEvent.touches) ? e.originalEvent.touches[0] : e;
  // Recording current positions
  startPosition = {x: e.pageX, y: e.pageY};
  elementPosition = {x: ball.offset().left, y: ball.offset().top};
  // These event listeners will be removed later
  ball.on('mousemove.rem touchmove.rem',function(e){
    e = (e.originalEvent.touches) ? e.originalEvent.touches[0] : e;
    ball.css({
      top:elementPosition.y + (e.pageY - startPosition.y),
      left: elementPosition.x + (e.pageX - startPosition.x),
    });
  });
});
ball.on('mouseup touchend',function(){
  // Removing the heavy *move listeners
  ball.off('.rem');
});

<a href="http://google.com/" id="goToGoogle">Go To Google</a>

$('#goToGoogle').click(false);

var press = $('#press');
press.on('click',function(){
  return 'Hip';
});
press.on('click',function(e){
  console.log(e.result + ' Hop!');
})
//控制台输出: HipHop!

$.when($.get('assets/misc/1.json'), $.get('assets/misc/2.json')).then(function(r1, r2){
  console.log(r1[0].message + " " + r2[0].message);
})

var contentDivs = $('.content');
contentDivs.eq(0).load('1.txt');
contentDivs.eq(1).load('1.html #header');

var ip = '119.75.218.70',
  api = 'http://freegeoip.net/json/' + ip + '?callback=?';
$.getJSON(api, function(r){
  console.log('How is the weather in ' + r.city + ', ' + r.country_name + '?');
});

(function($){
  var c = 1;
  $.fn.count = function(){
    log(c++);
    return this;
  }; 
})(jQuery);
$(document).count();
$('body').count().count();