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jQuery Deferred .promise() method
  • Last Updated : 16 Jul, 2020

This .promise() method in JQuery Returns a Promise object to be observed when certain type actions bounded to the collection, queued or not, are ended.

Syntax:

.promise([type][, target])

    Parameters:

  • type: This parameter specifies the type of queue which needed to be observed.
  • target: This parameter specifies Object onto which the promise methods need to be attached.

Return Value: This method returns a dynamically generated Promise which is resolved once actions bounded to the collection, queued or not, have finished.

There are two examples discussed below:

  • Example: In this example, the Deferred() is used to create a new object and after that then() method is called with notify and resolve method.




    <!DOCTYPE HTML> 
    <html>  
    <head>
        <title
          JQuery.when() method
        </title>
      </script
    </head>   
    <body style="text-align:center;">
        <h1 style="color:green">  
            GeeksForGeeks  
        </h1
        <p id="GFG_UP"
        </p>
        <button onclick = "Geeks();">
        click here
        </button>
        <p id="GFG_DOWN"
        </p>
        <script
            var el_up = document.getElementById("GFG_UP");
            el_up.innerHTML = "JQuery.when() method";
            var def = $.Deferred();
            function Geeks() {
                $.when().then(function(a) {
                  alert( "when() method called this alert()." );
                });
            
         </script
    </body>   
    </html>        

    Output:
    Before clicking on button:

    After clicking on button:

    • Example: In this example, the Deferred() method is used and the state of Deferred object is checked.




      <!DOCTYPE HTML> 
      <html>  
      <head>
          <title
            JQuery.when() method
          </title>
      </script
      </head>   
      <body style="text-align:center;">
          <h1 style="color:green">  
              GeeksForGeeks  
          </h1
          <p id="GFG_UP"
          </p>
          <button onclick = "Geeks();">
          click here
          </button>
          <p id="GFG_DOWN"
          </p>
          <script>
              var el_up = document.getElementById("GFG_UP");
              el_up.innerHTML = "JQuery.when() method";
              var def = $.Deferred();
              function Geeks() {
                  $.when(def).done(function (x) {
                    $('#GFG_DOWN').append('when() method is executed.')
                  });
                  def.resolve();
              
           </script
      </body>   
      </html>              

      Output:




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