【发布时间】：2013-05-16 11:47:51
【问题描述】：
所以我用一些 JavaScript 函数编写了一个网页。
该页面在 Dreamweaver 中完美运行，但当我在浏览器（Google Chrome 和 Firefox）中试用时，JavaScript 会闪烁一瞬间然后清除。我完全不知道为什么会这样。
<body>
<form name="myForm">
<ol>
<li>
<h1> TILE CALCULATOR</h1>
</li>
<li>
<label for="wall height">Wall height (cm)</label>
<input type="text" id="wall_height" />
</li>
<li>
<label for="wall width">Wall Width (cm)</label>
<input type="text" id="wall_width" />
</li>
<li>
<label for="tile height">Tile Height (cm)</label>
<input type="text" id="tile_height" />
</li>
<li>
<label for="tile width">Tile Width (cm)</label>
<input type="text" id="tile_width" />
</li>
<button onclick="javascript:validate();"> Calculate </button>
</ol>
</form>
<br />
<p id="result"></p>
<br />
<canvas id="myCanvas">
Your browser does not support this feature</canvas>
<br />
<br />
<script language="javascript" type="text/javascript">
//functoin to validate the inputs by the user
//user can only enter a number and all fields must be filled
function validate()
{
//first make sure canvas is clear
clearCanvas()
//take the inputs as variables
var x = document.getElementById("tile_width").value;
var y = document.getElementById("tile_height").value;
var z = document.getElementById("wall_width").value;
var i = document.getElementById("wall_height").value;
//check if the user has entered nothing and alert if they have
if (x==null || x=="" || y==null || y=="" || z==null || z=="" || i==null || i=="")
{
alert("All the fields have to be filled out!");
clearResult();
}
// check if the user has entered invalid values, only numbers can be entered
if (isNaN(x) == true || isNaN(y) == true || isNaN(z) == true || isNaN(i) == true)
{
alert("Dimensions can only be numbers!");
clearResult();
}
//check for negatives
if (x <= 0 || y <= 0 || z <= 0 || i <= 0)
{
alert("invalid dimension input, positive non-zero values only");
clearResult();
}
//if valid calculate tiles and print
else
tileCalculator();
}
function tileCalculator()
{
//take the input as variables
var tileWidth = document.getElementById("tile_width").value;
var tileHeight = document.getElementById("tile_height").value;
var wallWidth = document.getElementById("wall_width").value;
var wallHeight = document.getElementById("wall_height").value;
//find the areas of the tile and the wall
var tileArea = tileWidth * tileHeight;
var wallArea = wallWidth * wallHeight;
//divide these to find the number of tiles needed
var noOfTiles = (wallArea/tileArea);
//prints the result of noOfTiles
document.getElementById("result").innerHTML=" The number of Tiles you will need are : " + noOfTiles;
//scalled tiles to the canvas width of your choice
var scalledWidth = 500;
var ratioHW = wallHeight/wallWidth;
var scalledHeight = ratioHW*scalledWidth;
//scaled tile sizes
//scale the tiles to correct pixels
var scalledTileWidth = (tileWidth/wallWidth)*scalledWidth;
var scalledTileHeight = (tileHeight/wallHeight)*300;
//finds the number of tiles needs in a row
var noWidth = wallWidth/tileWidth;
//number of tiles in a column
var noHeight = wallHeight/tileHeight;
var canvas = document.getElementById("myCanvas");
canvas.style.width=scalledWidth + "px";
canvas.style.height=scalledHeight + "px";
printWall(0,0,noWidth,scalledTileWidth,(scalledTileHeight/2),noHeight);
}
//print a tile given the position and dimensions
function printTile(x,y,tileWidth,tileHeight)
{
var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");
ctx.fillRect(x,y,tileWidth,tileHeight);
}
//prints one row of tiles given the starting position and number to be printed
function printTileRow(x,y,numberOfTiles,tileWidth,tileHeight)
{
var start = 0;
//loops upto number of tiles in a row
while (start < numberOfTiles)
{
//prints a tile each time
printTile(x,y,tileWidth,tileHeight);
//next brick position
x = x + (tileWidth + 1); // add a space between tiles here.
start++;
}
}
//prints the wall
function printWall(x,y,numberOfTiles,tileWidth,tileHeight,numberOfRows)
{
//holds whether last row was shifted
var shiftCount = 0;
//starting index
var start = 0;
//loop up adding a row until required number of rows
while (start < numberOfRows)
{
//prints half a tile at the start of each row
printTile(0,y,(0.5 * tileWidth - 1),(tileHeight));
//prints the row
printTileRow((x+shiftCount),y,numberOfTiles,tileWidth,tileHeight);
//if shifted
if (shiftCount > 0)
{
//was shifted last row
shiftCount = 0;
}
else
{
//was not shifted last row
shiftCount = shiftCount + (0.5*tileWidth);
}
start++;
//start next row
y = y + (tileHeight + 1);
}
}
//clears the canvus each time the button is pressed
function clearCanvas()
{
//reset canvus to 300 by 300 and clear
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext('2d');
canvas.style.height="300px";
canvas.style.width="300px";
context.clearRect(0,0,300,300);
}
function clearResult()
{
document.getElementById("result").innerHTML="";
}
</script>
</body>
如果有人能快速找到我，我将不胜感激！谢谢，
【问题讨论】：
-
您的 javascript 的计划行为是什么？
-
它在画布上打印出一堵墙，并给出该区域的结果。它打印墙并在dreamweaver中给出结果然后停留在那里，在浏览器中打印并给出正确的结果，但只会在屏幕上闪烁一秒钟
标签： javascript html