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HTML5 drag-and-drop learning and complete example code

PHPz

Apr 23, 2017 am 11:55 AM

This article learns how to drag and drop HTML5 and complete the example code. I hope it will be helpful to H5 beginners!

1) Create the source project

1.1) The value of the draggable attribute:

true——this element Can be dragged;

false - this element cannot be dragged;

auto - the browser can independently determine an element Whether it can be dragged;

1.2) Events of dragged elements:

dragstart - triggered when the element starts to be dragged ；

drag——Triggered repeatedly when the element is dragged.

dragend——triggered when the drag operation is completed;

2) Create a release area

2.1) Release area event:

dragenter - triggered when the dragged element enters the screen space occupied by the release area;

Dragover——Triggered when the dragged element moves within the release area;

dragleave——Triggered when the dragged element leaves the release area without being placed;

Drop——Triggered when the dragged element is dropped in the release area.

<!DOCTYPE HTML>
<html>
    <head>
        <title>Example</title>
        <style>
            #src > * {float:left;}
            #src > img {border: thin solid black; padding: 2px; margin:4px;}
            #target {border: thin solid black; margin:4px;}
            #target { height: 81px; width: 81px; text-align: center; display: table;}
            #target > p {display: table-cell; vertical-align: middle;}
            img.dragged {background-color: lightgrey;}
        </style>
    </head>
    <body>
        <p id="src">
            <img draggable="true" id="banana" src="banana100.png" alt="banana"/>
            <img draggable="true" id="apple" src="apple100.png" alt="apple"/>
            <img draggable="true" id="cherries" src="cherries100.png" alt="cherry"/>
            <p id="target">
                <p id="msg">Drop Here</p>
            </p>            
        </p>            
    
        <script>
            var src = document.getElementById("src");
            var target = document.getElementById("target");
            var msg = document.getElementById("msg");
          
            var draggedID;
          
            target.ondragenter = handleDrag;
            target.ondragover = handleDrag;
            
            function handleDrag(e) {
                e.preventDefault();
            }
            
            target.ondrop = function(e) {
                var newElem = document.getElementById(draggedID).cloneNode(false);
                target.innerHTML = "";
                target.appendChild(newElem);
                e.preventDefault();
            }
          
            src.ondragstart = function(e) {
                draggedID = e.target.id;
                e.target.classList.add("dragged");
            }
            
            src.ondragend = function(e) {
                var elems = document.querySelectorAll(".dragged");
                for (var i = 0; i < elems.length; i++) {
                    elems[i].classList.remove("dragged");
                }
            }          
        </script>
    </body>
</html>

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3) Use the DataTransfer object

3.1) Dispatched at the same time as the event triggered by the drag-and-drop operation The object is DragEvent, which is derived from MouseEvent.

Additional attributes defined by the DragEvent object:

dataTransfer——Returns the object used for data transfer to the release area (DataTransfer);

3.2) Properties defined by the DataTransfer object:

types - the format of the returned data.

getData()——Returns data in the specified format;

setData(, )——Set the data in the specified format.

clearData()——Remove data in the specified format.

files - Returns the list of dragged files.

<!DOCTYPE HTML>
<html>
    <head>
        <title>Example</title>
        <style>
            #src > * {float:left;}
            #src > img {border: thin solid black; padding: 2px; margin:4px;}
            #target {border: thin solid black; margin:4px;}
            #target { height: 81px; width: 81px; text-align: center; display: table;}
            #target > p {display: table-cell; vertical-align: middle;}
            img.dragged {background-color: lightgrey;}
        </style>
    </head>
    <body>
        <p id="src">
            <img draggable="true" id="banana" src="banana100.png" alt="banana"/>
            <img draggable="true" id="apple" src="apple100.png" alt="apple"/>
            <img draggable="true" id="cherries" src="cherries100.png" alt="cherry"/>
            <p id="target">
                <p id="msg">Drop Here</p>
            </p>            
        </p>            
    
        <script>
            var src = document.getElementById("src");
            var target = document.getElementById("target");
                    
            target.ondragenter = handleDrag;
            target.ondragover = handleDrag;
            
            function handleDrag(e) {
                e.preventDefault();
            }
            
            target.ondrop = function(e) {
                var droppedID = e.dataTransfer.getData("Text");               
                var newElem = document.getElementById(droppedID).cloneNode(false);
                target.innerHTML = "";
                target.appendChild(newElem);
                e.preventDefault();
            }
          
            src.ondragstart = function(e) {
                e.dataTransfer.setData("Text", e.target.id);
                e.target.classList.add("dragged");
            }
            
            src.ondragend = function(e) {
                var elems = document.querySelectorAll(".dragged");
                for (var i = 0; i < elems.length; i++) {
                    elems[i].classList.remove("dragged");
                }
            }          
        </script>
    </body>
</html>

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3.3) Drag and drop files:

Properties defined by File object

name——Get the file name.

type——Get the file type. Represented by MIME type;

size——Get the file size (calculated in bytes);

<!DOCTYPE HTML>
<html>
    <head>
        <title>Example</title>
        <style>
            .table {display:table;}
            .row {display:table-row;}
            .cell {display: table-cell; padding: 5px;}
            .label {text-align: right;}
            #target {border: medium double black; margin:4px; height: 50px;
                width: 200px; text-align: center; display: table;}
            #target > p {display: table-cell; vertical-align: middle;}
        </style>
    </head>
    <body>
        <form id="fruitform" method="post" action="http://titan:8080/form">
            <p class="table">
                <p class="row">
                    <p class="cell label">Bananas:</p>
                    <p class="cell"><input name="bananas" value="2"/></p>
                </p>
                <p class="row">
                    <p class="cell label">Apples:</p>
                    <p class="cell"><input name="apples" value="5"/></p>
                </p>
                <p class="row">
                    <p class="cell label">Cherries:</p>
                    <p class="cell"><input name="cherries" value="20"/></p>
                </p>
                <p class="row">
                    <p class="cell label">File:</p>
                    <p class="cell"><input type="file" name="file"/></p>
                </p>
                <p class="row">
                    <p class="cell label">Total:</p>
                    <p id="results" class="cell">0 items</p>
                </p>                
            </p>
            <p id="target">
                <p id="msg">Drop Files Here</p>
            </p>            
            <button id="submit" type="submit">Submit Form</button>
        </form>
        <script>
            var target = document.getElementById("target");     
            var httpRequest;
            var fileList;
                         
            document.getElementById("submit").onclick = handleButtonPress;                    
            target.ondragenter = handleDrag;
            target.ondragover = handleDrag;
            
            function handleDrag(e) {
                e.preventDefault();
            }
            
            target.ondrop = function(e) {
                fileList = e.dataTransfer.files;
                e.preventDefault();
            }          
                         
            function handleButtonPress(e) {
                e.preventDefault();
                 
                var form = document.getElementById("fruitform");
                var formData = new FormData(form);
                 
                if (fileList || true) {
                    for (var i = 0; i < fileList.length; i++) {
                        formData.append("file" + i, fileList[i]);
                    }
                }  
                 
                httpRequest = new XMLHttpRequest();
                httpRequest.onreadystatechange = handleResponse;
                httpRequest.open("POST", form.action);
                httpRequest.send(formData);
            }
                         
            function handleResponse() {
                if (httpRequest.readyState == 4 && httpRequest.status == 200) {
                    var data = JSON.parse(httpRequest.responseText);
                    document.getElementById("results").innerHTML = "You ordered "
                        + data.total + " items";
                }
            }
         </script>
    </body>
</html>

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