Using Drag-Related Event Handlers

Using Drag-Related Event Handlers : Mouse Event : Event onMethod JAVASCRIPT DHTML TUTORIALS

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Using Drag-Related Event Handlers




/*
JavaScript Bible, Fourth Edition
by Danny Goodman 

John Wiley & Sons CopyRight 2001
*/


<HTML>
<HEAD>
<TITLE>Dragging Event Handlers</TITLE>
<STYLE TYPE="text/css">
TD {text-align:center}
TH {text-decoration:underline}
.blanks {text-decoration:underline}
</STYLE>

<SCRIPT LANGUAGE="JavaScript">
var timer
function setupDrag() {
    if (event.srcElement.tagName != "TD") {
        // don't allow dragging for any other elements
        event.returnValue = false
    } else {
        // setup array of data to be passed to drop target
        var passedData = [event.srcElement.innerText, event.srcElement.className]
        // store it as a string
        event.dataTransfer.setData("Text", passedData.join(":"))
        event.dataTransfer.effectAllowed = "copy"
        timer = new Date()
    }
}
function timeIt() {
    if (event.srcElement.tagName == "TD" && timer) {
        if ((new Date()) - timer > 2000) {
            alert("Sorry, time is up. Try again.")
            timer = 0
        }
    }
}
function handleDrop() {
    var elem = event.srcElement
    var passedData = event.dataTransfer.getData("Text")
    var errMsg = ""
    if (passedData) {
        // reconvert passed string to an array
        passedData = passedData.split(":")
        if (elem.id == "blank1") {
            if (passedData[1] == "noun") {
                event.dataTransfer.dropEffect = "copy"
                event.srcElement.innerText = passedData[0]
            } else {
                errMsg = "You can't put an adjective into the noun placeholder."
            }
        } else if (elem.id == "blank2") {
            if (passedData[1] == "adjective") {
                event.dataTransfer.dropEffect = "copy"
                event.srcElement.innerText = passedData[0]
            } else {
                errMsg = "You can't put a noun into the adjective placeholder."
            }
        }
        if (errMsg) {
            alert(errMsg)
        }
    }
}
function cancelDefault() {
    if (event.srcElement.id.indexOf("blank") == 0) {
        event.dataTransfer.dropEffect = "copy"
        event.returnValue = false
    }
}
</SCRIPT>
</HEAD>
<BODY onDragStart="setupDrag()" onDrag="timeIt()">
<H1>Dragging Event Handlers</H1>
<HR>
<P>Your goal is to drag one noun and one
adjective from the following table into the blanks
of the sentence. Select a word from the table and
drag it to the desired blank. When you release the
mouse, the word will appear in the blank. You have
two seconds to complete each blank.</P>
<TABLE CELLPADDING=5>
<TR><TH>Nouns</TH><TH>Adjectives</TH></TR>
<TR><TD class="noun">truck</TD><TD class="adjective">round</TD></TR>
<TR><TD class="noun">doll</TD><TD class="adjective">red</TD></TR>
<TR><TD class="noun">ball</TD><TD class="adjective">pretty</TD></TR>
</TABLE>
<P ID="myP" onDragEnter="cancelDefault()" onDragOver="cancelDefault()"
 onDrop="handleDrop()">
Pat said, "Oh my, the <SPAN ID="blank1" CLASS="blanks">
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</SPAN> 
is so <SPAN ID="blank2" CLASS="blanks">
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</SPAN>!"</P>
<BUTTON onClick="location.reload()">Reset</BUTTON>
</BODY>
</HTML>