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Thread: How can I add an button to erase the entire drawing surface?

  1. #1
    Join Date
    Apr 2012

    How can I add an button to erase the entire drawing surface?

    Thanks for the help guys!! Here is the code....

    <html xmlns="http://www.w3.org/1999/xhtml">

    <title>Simple Drawing Program</title>
    <style type="text/css">
    /* #canvas selects the elemnet with id="canvas" */
    width: 400px;
    border: 1px solid #999999;
    border-collapse: collapse;

    width: 4px;
    height: 4px;

    font-family: arial, helvetica, sans-serif;
    font-size: 12px;
    border-bottom: 1px solid #999999;


    <script type="text/javascript">
    //initialization function to insert cells into the table
    function createCanvas() {//======================================================
    var side = 100;
    //IE will not dynamically (i.e. in script) append rows directly to a <table> but will do so to a <tbody>
    var tbody = document.getElementById("tablebody");

    for (var i = 0; i < side; i++) {
    var row = document.createElement("tr"); // row is reused to reference each new row

    for (var j = 0; j < side; j++) {
    var cell = document.createElement("td"); // cell is reused to reference each new cell

    cell.onmousemove = processMouseMove; // register event handler traditionally

    } // end for each cell

    } // end for each row


    // processes the onmousemove event
    function processMouseMove(e) {//================================================
    // if FF e will be available as formal parameter (i.e. DOM2 compliant)
    if (!e)
    var e = window.event; // if IE no e but can use window.event (i.e. NOT DOM2 compliant)

    // e now cross-browser compliant

    // turn the cell blue if the Ctrl key is pressed
    if (e.ctrlKey)
    this.style.backgroundColor = "blue"; // this is the <td> the mouse is currently moving over i.e. the element that caused this script to execute

    // turn the cell red if the Shift key is pressed
    if (e.shiftKey)
    this.style.backgroundColor = "red";

    if (e.altKey)
    this.style.backgroundColor = "White";
    } // end function processMouseMove
    function erase() {



    // -->



    <!-- colspan: number of columns to extend <th> or <td> over, <tt> monospace font -->
    <body onload="createCanvas()">
    <table id="canvas">
    <tbody id="tablebody">
    <th class="key" colspan="100">
    Hold <tt>ctrl</tt> to draw blue. Hold <tt>shift</tt> to draw red.
    Hold <tt>alt</tt> to erase.

    <input id="erase" type="button" value="Erase the background" onclick="erase()" />


  2. #2
    Join Date
    Oct 2006
    IE loads the page very slow and runs the erase function a bit faster.
    Firefox doesn't have a problem

    HTML Code:
    function erase() {
    	var tb=document.getElementsByTagName('table');
    	var tbc=tb[0].getElementsByTagName('td'); 

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