最高のjQueryの例

jQueryは最も広く使用されているJavaScriptライブラリであり、すべての主要なWebサイトの半分以上で使用されています。それは「書くことを減らし、もっとすること...!」をモットーにしています。

jQueryは、多数の「ヘルパー」関数を提供することにより、Web開発をより使いやすくします。これらは、開発者がJavaScript自体を手動で作成しなくても、DOM(Document Object Model)インタラクションをすばやく作成するのに役立ちます。

jQueryは、すべてのライブラリメソッドがアタッチされたグローバル変数を追加します。命名規則では、このグローバル変数を$。入力する$.ことで、すべてのjQueryメソッドを自由に使用できます。

入門

jQueryの使用を開始する主な方法は2つあります。

  • jQueryをローカルに含める:jquery.comからjQueryライブラリをダウンロードし、HTMLコードに含めます。
  • CDNを使用する:CDN(コンテンツ配信ネットワーク)を使用してjQueryライブラリにリンクします。

セレクター

jQueryは、CSSスタイルのセレクターを使用してHTMLページのパーツまたは要素を選択します。次に、jQueryメソッドまたは関数を使用して要素で何かを実行できます。

これらのセレクターの1つを使用するには、ドル記号とその後ろの括弧を入力します$()。これはjQuery()関数の省略形です。括弧内に、選択する要素を追加します。一重引用符または二重引用符のいずれかを使用できます。この後、括弧と使用するメソッドの後にドットを追加します。

jQueryでは、クラスセレクターとIDセレクターはCSSのものと似ています。

これは、すべての段落要素を選択し、それらに「selected」のクラスを追加するjQueryメソッドの例です。

This is a paragraph selected by a jQuery method.

This is also a paragraph selected by a jQuery method.

$("p").addClass("selected");

jQueryでは、クラスセレクターとIDセレクターはCSSと同じです。特定のクラスの要素を選択する場合は、ドット(.)とクラス名を使用します。特定のIDを持つ要素を選択する場合は、ハッシュ記号(#)とID名を使用します。HTMLでは大文字と小文字が区別されないため、HTMLマークアップとCSSセレクターは小文字のままにしておくことをお勧めします。

クラス別選択

特定のクラスの要素を選択する場合は、ドット(。)とクラス名を使用します。

Paragraph with a class.

$(".pWithClass").css("color", "blue"); // colors the text blue

クラスセレクターをタグ名と組み合わせて使用​​して、より具体的にすることもできます。

    My Wish List
`

$("ul.wishList").append("
  • New blender
  • ");

    IDで選択

    特定のID値を持つ要素を選択する場合は、ハッシュ記号(#)とID名を使用します。

  • List item with an ID.
  • $("#liWithID").replaceWith("

    Socks

    ");

    クラスセレクターと同様に、これはタグ名と組み合わせて使用​​することもできます。

    News Headline

    $("h1#headline").css("font-size", "2em");

    属性値による選択

    特定の属性を持つ要素を選択する場合は、を使用します([attributeName="value"])

    $("[name='myInput']").value("Test"); // sets input value to "Test"

    属性セレクターをタグ名と組み合わせて使用​​して、より具体的にすることもできます。

    `

    Button

    $("input[name='myElement']").remove(); // removes the input field not the button

    フィルタとして機能するセレクタ

    フィルタとして機能するセレクタもあります。通常、コロンで始まります。たとえば、:firstセレクターは、その親の最初の子である要素を選択します。これは、いくつかのリスト項目を含む順序付けされていないリストの例です。リストの下のjQueryセレクターは最初のものを選択します

  • リスト内の要素(「1つ」のリスト項目)を使用して、.cssメソッドを使用してテキストを緑色にします。

    • One
    • Two
    • Three
    $("li:first").css("color", "green");

    属性セレクター

    There are selectors that return elements which matches certain combinations of Attributes like Attribute contains, Attribute ends with, Attribute starts with etc. Here's an example of an unordered list with some list items. The jQuery selector below the list selects the

  • element in the list--the "One" list item as it has data* attribute as "India" as its value--and then uses the .css method to turn the text green.

    • Mumbai
    • Beijing
    • New York
    $("li[data-country='India']").css("color", "green");

    Another filtering selector, :contains(text), selects elements that have a certain text. Place the text you want to match in the parentheses. Here's an example with two paragraphs. The jQuery selector takes the word "Moto" and changes its color to yellow.

    Hello

    World

    $("p:contains('World')").css("color", "yellow");

    Similarly, the :last selector selects the element that is the last child of its parent. The jQuery selector below selects the last

  • Original text


  • element in the list--the "Three" list item--and then uses the .css method to turn the text yellow.

    $("li:last").css("color", "yellow");

    Note: In the jQuery selector, World is in single-quotes because it is already inside a pair of double-quotes. Always use single-quotes inside double-quotes to avoid unintentionally ending a string.

    Multiple Selectors

    In jQuery, you can use multiple selectors to apply the same changes to more than one element, using a single line of code. You do this by separating the different ids with a comma. For example, if you want to set the background color of three elements with ids cat,dog,and rat respectively to red, simply do:

    $("#cat,#dog,#rat").css("background-color","red");

    HTML Method

    The jQuery .html() method gets the content of a HTML element or sets the content of an HTML element.

    Getting

    To return the content of a HTML element, use this syntax:

    $('selector').html();

    For example:

    $('#example').html();

    Setting

    To set the content of a HTML element, use this syntax:

    $('selector').html(content);

    For example:

    $('p').html('Hello World!');

    That will set the content of all of the

    Warning

    .html() method is used to set the element's content in HTML format. This may be dangerous if the content is provided by user. Consider using .text() method instead if you need to set non-HTML strings as content.

    CSS Method

    The jQuery .css() method gets the value of a computed style property for the first element in the set of matched elements or set one or more CSS properties for every matched element.

    Getting

    To return the value of a specified CSS property, use the following syntax:

     $(selector).css(propertyName);

    Example:

     $('#element').css('background');

    Note: Here we can use any css selector eg: element(HTML Tag selector), .element(Class Selector), #element(ID selector).

    Setting

    To set a specified CSS property, use the following syntax:

     $(selector).css(propertyName,value);

    Example:

     $('#element').css('background','red');

    To set multiple CSS properties, you'll have to use the object literal syntax like this:

     $('#element').css({ 'background': 'gray', 'color': 'white' });

    If you want to change a property labeled with more than one word, refer to this example:

    To change background-color of an element

     $('#element').css('background-color', 'gray');

    Click Method

    The jQuery Click method triggers a function when an element is clicked. The function is known as a "handler" because it handles the click event. Functions can impact the HTML element that is bound to the click using the jQuery Click method, or they can change something else entirely. The most-used form is:

    $("#clickMe").click(handler)

    The click method takes the handler function as an argument and executes it every time the element #clickMe is clicked. The handler function receives a parameter known as an eventObject that can be useful for controlling the action.

    Examples

    This code shows an alert when a user clicks a button:

    Click Here
    $("#alert").click(function () { alert("Hi! I'm an alert"); });

    The eventObject has some built in methods, including preventDefault(), which does exactly what it says - stops the default event of an element. Here we pevent the anchor tag from acting as a link:

    Link to Google
    $("#myLink").click(function (event) { event.preventDefault(); });

    More ways to play with the click method

    The handler function can also accept additional data in the form of an object:

    jqueryElement.click(usefulInfo, handler)

    The data can be of any type.

    $("element").click({firstWord: "Hello", secondWord: "World"}, function(event){ alert(event.data.firstWord); alert(event.data.secondWord); });

    Invoking the click method without a handler function triggers a click event:

    $("#alert").click(function () { alert("Hi! I'm an alert"); }); $("#alert").click();

    Now, whenever the page loads, the click event will be triggered when we enter or reload the page, and show the assigned alert.

    Also you should prefer to use .on("click",...) over .click(...) because the former can use less memory and work for dynamically added elements.

    Common Mistakes

    The click event is only bound to elements currently in the DOM at the time of binding, so any elements added afterwards will not be bound. To bind all elements in the DOM, even if they will be created at a later time, use the .on() method.

    For example, this click method example:

    $("element").click(function() { alert("I've been clicked!"); });

    Can be changed to this on method example:

    $(document).on("click", "element", function() { alert("I've been clicked!"); });

    Getting The Element From A Click event

    This applies to both jQuery and plain JavaScript, but if you set up your event trigger to target a class, you can grab the specific element that triggered the element by using the this keyword.

    jQuery happens to make it very easy (and multi browser friendly) to traverse the DOM to find that element's parents, siblings, and children, as well.

    Let's say I have a table full of buttons and I want to target the row that button is in, I can simply wrap this in a jQuery selector and then get its parent and its parent's parent like so:

    $( document ).on("click", ".myCustomBtnClassInATable", function () { var myTableCell = $(this).parent(); var myTableRow = myTableCell.parent(); var myTableBody = myTableRow.parent(); var myTable = myTableBody.parent(); //you can also chain these all together to get what you want in one line var myTableBody = $(this).parent().parent().parent(); });

    It is also interesting to check out the event data for the click event, which you can grab by passing in any variable name to the function in the click event. You'll most likely see an e or event in most cases:

    $( document ).on("click", ".myCustomBtnClassInATable", function (e) { //find out more information about the event variable in the console console.log(e); });

    Mousedown Method

    The mousedown event occurs when the left mouse button is pressed. To trigger the mousedown event for the selected element, use this syntax: $(selector).mousedown();

    Most of the time, however, the mousedown method is used with a function attached to the mousedown event. Here's the syntax: $(selector).mousedown(function); For example:

    $(#example).mousedown(function(){ alert("Example was clicked"); });

    That code will make the page alert "Example was clicked" when #example is clicked.

    Hover Method

    The jquery hover method is a combination of the mouseenter and mouseleave events. The syntax is this:

    $(selector).hover(inFunction, outFunction);

    The first function, inFunction, will run when the mouseenter event occurs. The second function is optional, but will run when the mouseleave event occurs. If only one function is specified, the other function will run for both the mouseenter and mouseleave events. Below is a more specific example.

    $("p").hover(function(){ $(this).css("background-color", "yellow"); }, function(){ $(this).css("background-color", "pink"); });

    So this means that hover on paragraph will change its background color to yellow and the opposite will change back to pink.

    Animate Method

    jQuery's animate method makes it easy to create simple animations using only a few lines of code. The basic structure is as following:

    $(".selector").animate(properties, duration, callbackFunction());

    For the properties argument, you need to pass a javascript object with the CSS properties you want to animate as keys and the values you want to animate to as values. For the duration, you need to input the amount of time in milliseconds the animation should take. The callbackFunction() is executed once the animation has finished.

    Example

    A simple example would look like this:

    $(".awesome-animation").animate({ opacity: 1, bottom: += 15 }, 1000, function() { $(".different-element").hide(); });

    Hide Method

    In its simplest form, .hide() hides the matched element immediately, with no animation. For example:

    $(".myclass").hide()

    will hide all the elements whose class is myclass. Any jQuery selector can be used.

    .hide() as an animation method

    Thanks to its options, .hide() can animate the width, height, and opacity of the matched elements simultaneously.

    • Duration can be provided in milliseconds, or using the literals slow (600 ms) and fast(200ms). for example:
    • A function can be specified to be called once the animation is complete, once per every matched element. This callback is mainly useful for chaining together different animations. For example
    $("#myobject").hide(800)
    $("p").hide( "slow", function() { $(".titles").hide("fast"); alert("No more text!"); });

    Show Method

    In its simplest form, .show() displays the matched element immediately, with no animation. For example:

    $(".myclass").show();

    will show all the elements whose class is myclass. Any jQuery selector can be used.

    However, this method does not override !important in the CSS style, such as display: none !important.

    .show() as an animation method

    Thanks to its options, .show() can animate the width, height, and opacity of the matched elements simultaneously.

    • Duration can be provided in milliseconds, or using the literals slow (600 ms) and fast(200ms). for example:
    • A function can be specified to be called once the animation is complete, once per every matched element. for example
    $("#myobject").show("slow");
    $("#title").show( "slow", function() { $("p").show("fast"); });

    jQuery Toggle method

    To show / hide elements you can use toggle() method. If element is hidden toggle() will show it and vice versa. Usage:

    $(".myclass").toggle()

    Slide Down method

    This method animates the height of the matched elements. This causes lower parts of the page to slide down, making way for the revealed items. Usage:

    $(".myclass").slideDown(); //will expand the element with the identifier myclass for 400 ms. $(".myclass").slideDown(1000); //will expand the element with the identifier myclass for 1000 ms. $(".myclass").slideDown("slow"); //will expand the element with the identifier myclass for 600 ms. $(".myclass").slideDown("fast"); //will expand the element with the identifier myclass for 200 ms.

    Load Method

    The load() method loads data from a server and puts the returned data into the selected element.

    Note: There is also a jQuery Event method called load. Which one is called, depends on the parameters.

    Example

    $("button").click(function(){ $("#div1").load("demo_test.txt"); });

    Chaining

    jQuery chaining allows you to execute multiple methods on the same jQuery selection, all on a single line.

    Chaining allows us to turn multi-line statements:

    $('#someElement').removeClass('classA'); $('#someElement').addClass('classB');

    Into a single statement:

    $('#someElement').removeClass('classA').addClass('classB');

    Ajax Get Method

    Sends an asynchronous http GET request to load data from the server. Its general form is:

    jQuery.get( url [, data ] [, success ] [, dataType ] )
    • url: The only mandatory parameter. This string contains the address to which to send the request. The returned data will be ignored if no other parameter is specified.
    • data: A plain object or string sent to the server with the request.
    • success: A callback function executed if the request succeeds. It takes as an argument the returned data. It is also passed the text status of the response.
    • dataType: The type of data expected from the server. The default is Intelligent Guess (xml, json, script, text, html). If this parameter is provided, the success callback also must be provided.

    Examples

    Request resource.json from the server, send additional data, and ignore the returned result:

    $.get('//example.com/resource.json', {category:'client', type:'premium'});

    Request resource.json from the server, send additional data, and handle the returned response (json format):

    $.get('//example.com/resource.json', {category:'client', type:'premium'}, function(response) { alert("success"); $("#mypar").html(response.amount); });

    However, $.get doesn't provide any way to handle error.

    The above example (with error handling) can also be written as:

    $.get('//example.com/resource.json', {category:'client', type:'premium'}) .done(function(response) { alert("success"); $("#mypar").html(response.amount); }) .fail(function(error) { alert("error"); $("#mypar").html(error.statusText); });

    Ajax GET Equivalent

    $.get( url [, data ] [, success ] [, dataType ] ) is a shorthand Ajax function, equivalent to:

    $.ajax({ url: url, data: data, success: success, dataType: dataType });

    Ajax Post Method

    Sends an asynchronous http POST request to load data from the server. Its general form is:

    jQuery.post( url [, data ] [, success ] [, dataType ] )
    • url : This is the only mandatory parameter. This string contains the adress to which to send the request. The returned data will be ignored if no other parameter is specified
    • data : A plain object or string that is sent to the server with the request.
    • success : A callback function that is executed if the request succeeds. It takes as an argument the returned data. It is also passed the text status of the response.
    • dataType : The type of data expected from the server. The default is Intelligent Guess (xml, json, script, text, html). if this parameter is provided, then the success callback must be provided as well.

    Examples

    $.post('//example.com/form.php', {category:'client', type:'premium'});

    requests form.php from the server, sending additional data and ignoring the returned result

    $.post('//example.com/form.php', {category:'client', type:'premium'}, function(response){ alert("success"); $("#mypar").html(response.amount); });

    requests form.php from the server, sending additional data and handling the returned response (json format). This example can be written in this format:

    $.post('//example.com/form.php', {category:'client', type:'premium'}).done(function(response){ alert("success"); $("#mypar").html(response.amount); });

    The following example posts a form using Ajax and put results in a div

        jQuery.post demo // Attach a submit handler to the form $( "#searchForm" ).submit(function( event ) { // Stop form from submitting normally event.preventDefault(); // Get some values from elements on the page: var $form = $( this ), term = $form.find( "input[name='s']" ).val(), url = $form.attr( "action" ); // Send the data using post var posting = $.post( url, { s: term } ); // Put the results in a div posting.done(function( data ) { var content = $( data ).find( "#content" ); $( "#result" ).empty().append( content ); }); });   

    The following example use the github api to fetch the list of repositories of a user using jQuery.ajax() and put results in a div

        jQuery Get demo // Attach a submit handler to the form $( "#userForm" ).submit(function( event ) { // Stop form from submitting normally event.preventDefault(); // Get some values from elements on the page: var $form = $( this ), username = $form.find( "input[name='username']" ).val(), url = "//api.github.com/users/"+username+"/repos"; // Send the data using post var posting = $.post( url, { s: term } ); //Ajax Function to send a get request $.ajax({ type: "GET", url: url, dataType:"jsonp" success: function(response){ //if request if made successfully then the response represent the data $( "#result" ).empty().append( response ); } }); });   

    Ajax POST Equivalent

    $.post( url [, data ] [, success ] [, dataType ] ) is a shorthand Ajax function, equivalent to:

    $.ajax({ type: "POST", url: url, data: data, success: success, dataType: dataType });