JavaScript 移动延迟和多次击键

Question

这是我的问题：http : //testepi.kvalitne.cz/test/

我不想要按键和方块移动之间的延迟。我也想知道如何对角移动（同时按下两个键）。

我的代码：

$(function(){

document.addEventListener("keydown", move, false);

var x = 0;
var y = 0;

function move(event){
  if(event.keyCode==37){
        x -= 10;
  $("#square").css("left", x);
  }

  if(event.keyCode==39){
        x += 10;
  $("#square").css("left", x);
  }

  if(event.keyCode==38){
        y -= 10;
  $("#square").css("top", y);
  }

  if(event.keyCode==40){
        y += 10;
  $("#square").css("top", y);
  }

}

});

Answer 1

首先，为了避免按键/重复延迟，您必须将程序包装在一个循环中，并使键盘的状态在该循环的范围内可用，其次要监视多个按键，您需要跟踪单个 keydown 和 keyup事件：

var x = 0;
var y = 0;

// store the current pressed keys in an array
var keys = [];

// if the pressed key is 38 (w) then keys[38] will be true
// keys [38] will remain true untill the key is released (below)
// the same is true for any other key, we can now detect multiple
// keypresses
$(document).keydown(function (e) {
    keys[e.keyCode] = true;
});

$(document).keyup(function (e) {
    delete keys[e.keyCode];
});
// we use this function to call our mainLoop function every 200ms
// so we are not relying on the key events to move our square
setInterval( mainLoop , 200 );

function mainLoop() {
     // here we query the array for each keyCode and execute the required actions
     if(keys[37]){
        x -= 10;
        $("#square").css("left", x);
     }

     if(keys[39]){
        x += 10;
        $("#square").css("left", x);
     }

     if(keys[38]){
        y -= 10;
        $("#square").css("top", y);
     }

     if(keys[40]){
        y += 10;
        $("#square").css("top", y);
     }
}