jQuery is a lightweight, "write less, do more", JavaScript library.

The purpose of jQuery is to make it much easier to use JavaScript on your website.

jQuery selectors and Actions are the important parts of the jQuery library.

1. The #id Selector

$(document).ready(function(){
  $("button").click(function(){
    $("#test").hide();
  });
});

2. The .class Selector

$(document).ready(function(){
  $("button").click(function(){
    $(".test").hide();
  });
});

3.  jQuery hide() and show()

$("#hide").click(function(){
  $("p").hide();
});

$("#show").click(function(){
  $("p").show();
});

4.  jQuery animate()

$("button").click(function(){
  $("div").animate({left: '250px'});
}); 

5.  jQuery Get 

$("#btn1").click(function(){
  alert("Text: " + $("#test").text());
});

6. jQuery Set

$("#btn1").click(function(){
  $("#test1").text("Invalid password!");
});

7.  jQuery append()

$("#btn1").click(function(){
  $("p").append("Some appended text.");
});

8.  jQuery prepend()

$("#btn1").click(function(){
  $("p").prepend("Some prepended text.");
});

JavaScript is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS.

DEMO 1 (You can try to refresh page in DEMO 1)