这是我使用箭头键使宇宙飞船移动的代码,我需要阻止将此元素(宇宙飞船)移出页面范围吗?
我的意思是当按下键时,元素会向下移动我不需要,请这是我的代码:
$(document).keydown(function(e){
$("body").innerWidth()
switch (e.which){
case 37: //left arrow key
$(".box").finish().animate({
left: "-=50"
});
break;
case 38: //up arrow key
$(".box").finish().animate({
top: "-=50"
});
break;
case 39: //right arrow key
$(".box").finish().animate({
left: "+=50"
});
break;
case 40: //bottom arrow key
$(".box").finish().animate({
top: "+=50"
});
break;
}
样式:
.box{
position: relative;
top: 10px;
width: 130px;
height: 130px;
position: relative;
margin: 200px auto 0;
background: url("http://davidpapp.com/wp-content/uploads/2015/05/rocket.png") ;
}
最佳答案
花点时间检查脚本的逻辑。按下按钮时,它只会移动对象,而不管它在页面上的位置。相反,您应该在执行实际移动之前包含一个条件来检查它是否可以/应该移动。
$(document).keydown(function(e){
var width = $("body").innerWidth();//Assigned this value to a variable
var height = $('body').height();//Created a variable for the height
var $box = $('.box');//Because I hate typing this so many times
var posX = parseFloat($box.css('left'));
var posY = parseFloat($box.css('top'));
switch (e.which) {
case 37: //left arrow key
//Don't allow if moving to the left would cause it to go less than 0
if(posX - 50 >= 0) {
$box.finish().animate({
left: "-=50"
});
}
break;
case 38: //up arrow key
//Don't allow if moving up would cause it to go less than 0
if(posY - 50 >= 0) {
$box.finish().animate({
top: "-=50"
});
}
break;
case 39: //right arrow key
//Not only checking to make sure the origin doesn't go over the width
//but also keep the width of the box in mind so it appears to stay within bounds
if(posX + 50 + $box.width() <= width) {
$box.finish().animate({
left: "+=50"
});
}
break;
case 40: //bottom arrow key
//Not only checking to make sure the origin doesn't go past the bottom line
//but also keep the height of the box in mind so it appears to stay within bounds
if(posY + 50 + $box.height() <= height) {
$box.finish().animate({
top: "+=50"
});
}
break;
}
}
附言我很快就写了这篇文章并且没有测试,所以如果我犯了拼写错误或者混淆了小于号和大于号,请不要感到惊讶,哈哈。无论如何,我希望您理解我试图传达的逻辑。
关于javascript - 为html中的元素制作边框 block ,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43455625/