使用addEventListener添加带有参数的回调 [英] Using addEventListener to add a callback with arguments

问题描述

我正在使用画布创建拖放系统。

I'm creating a drag and drop system using a canvas.

      canvas.addEventListener('mousedown', function () {
          window.initialClickX = mouse.x;
          window.initialClickY = mouse.y;
          window.initialBallX = ball.x;
          window.initialBallY = ball.y;
          canvas.addEventListener('mousemove', onMouseMove, false);
      }, false);

     function onMouseMove(){
        ball.x = mouse.x + window.initialBallX - window.initialClickX;
        ball.y = mouse.y + window.initialBallY - window.initialClickY;
        draw();
     }

当我点击，我需要存储初始鼠标位置的值，

When I click, I need to store the values for the initial mouse position and the initial ball position, so I can correctly drag the ball around.

上面的代码工作得很完美，但我认为它看起来很乱，所有的全局变量。我想让onMouseMove能够接受参数initialClickX，initialClickY，initialBallX和initialBallY。但是如何将这些参数添加到回调函数？

The above code works perfectly, but I think it looks messy with all the global variables. I'd like onMouseMove to be able to accept the parameters initialClickX, initialClickY, initialBallX and initialBallY. But how can I add these parameters to the callback function?

或者如果有更好的方法，请让我知道，谢谢。

Or if there is a better way to do this please let me know, thanks.

推荐答案

尝试使用包装器函数。

canvas.addEventListener('mousedown', function () {
      var initialClickX = mouse.x;
      var initialClickY = mouse.y;
      var initialBallX = ball.x;
      var initialBallY = ball.y;

      canvas.addEventListener('mousemove', function() {
          onMouseMove(initialClickX, initialClickY, mouse.x, mouse.y, initialBallX, initialBallY)
      }, false);

}, false);

function onMouseMove(initialClickX, initialClickY, mouseX, mouseY, initialBallX, initialBallY){
    ball.x = mouseX + initialBallX - initialClickX;
    ball.y = mouseY + initialBallY - initialClickY;
    draw();
}

这篇关于使用addEventListener添加带有参数的回调的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！