Question

我之前的程序反弹球，但现在我希望用户能够随时上下左右移动它。到目前为止，我的向右和向下按钮都工作，但我左右的逻辑没有。

在我看来，以下代码是正确的，但我猜它不是

我目前没有错误。球根本不动。

Answer 1

Here are some suggestions.

Create a single

result2 = animals.filter(function (value) {
    // letter filter
}).filter(function (value) {
    // length filter
});

function, which moves the ball a given move or x amount, and then calls itself using a timer:

You could then have a single function that handles all the movement buttons:

function move(x, y) {
  //movement code   
  moveBall= setTimeout(function() {
    move(x, y);
  },20);
}

Instead of determining the current position of the ball and adding an offset, use jQuery's $('.btn-primary').click(function() { $('.btn-primary').prop('disabled', false); $(this).prop('disabled', true); clearInterval(moveBall); switch(this.id) { case 'moveU': move(0, -velocity_y); break; case 'moveD': move(0, velocity_y); break; case 'moveL': move(-velocity_x, 0); break; case 'moveR': move( velocity_x, 0); break; } }); syntax for changing by a relative amount (css()):

+=

If the ball is outside its container, simply reverse the relative direction (

$('#ball').css({
  top : '+=' + y,
  left: '+=' + x
});

):

-=

I've put these suggestions together in this Fiddle:

http://jsfiddle.net/s1v128Lh/

Answer 2

你改变了太多：只需复制，例如，moveR（）并用减号替换加号： https://jsfiddle.net/svArtist/pnuqyyqh/

    function moveL() {
    // Read the current left position of the ball
    var currentLeftPos = parseInt($("#ball").css('left'));

    // define the new position
    var newLeftPos = currentLeftPos - velocity_x;

    // If the left position is greater than or equal to the maximum distance allowed or
    //   less than or equal to zero, then change the direction.

    if( newLeftPos >= maxLeft || newLeftPos <= 0)
        velocity_x *= 0; // multiply the value by -1

    // update the position
    $("#ball").css('left', newLeftPos + 'px');

    // display number of seconds played


  }

向上和向右移动球

2 个答案: