Question

我有一个网格，我正在尝试将光标编程到，网格中有一个中心点，我试图让光标只能从该中心点移动x个方块，这里是代码我有

var makecursor = function (axis, operation) {
    oppositeAxis = axis === 'y' ? 'x' : 'y';

    // app.cursor contains the x and y coordinates of the cursor
    app.cursor[axis] = 

    // calcualte the difference between the current cursor location and the origin
    Math.abs( app.cursor[axis] - origin[axis] ) + 

   // calculate the difference between the opposite axis and
   // the origin and add it to the previous calculation
    Math.abs( app.cursor[oppositAxis] - origin[oppositeAxis] ) 

  // add the operation to be performed ( movement of cursor, 1 or -1 )
  + operation 

  // if the sum of the x, y and current operation are greater then the allowed
  // movement, then make "app.cursor[axis]" equal to itself (dont move) , 
  // otherwise make "app.cursor[axis]" equal to itself plus the operation ( move )

> origin.movement ? app.cursor[axis] : app.cursor[axis] + operation;
}

“operation”为1或-1，用于方向性

“origin.movement”是您可以移动光标的原点的方格数。

我希望/期望的行为是从我的网格上的一个正方形，你只能在“origin.movement”变量中指定多个正方形。但是当我打印出结果时它返回奇怪的数字，并且它没有正确计算位置，即原点应该为零，而是取而代之前的一个或两个，取决于先前的运动，我还没有其他许多异常能够理解。任何有关这个问题的帮助将不胜感激，谢谢！

Answer 1

你需要在正在测试> origin.movement的表达式周围放置一些parens，以便在那里使用该表达式的结果;如果没有它们，表达式就会被打破：

var makecursor = function (axis, operation) {
    var oppositeAxis = axis === 'y' ? 'x' : 'y';

    app.cursor[axis] = (
        // calculate the difference between the current cursor location and the origin
        Math.abs( app.cursor[axis] - origin[axis] ) + 

        // calculate the difference between the opposite axis and
        // the origin and add it to the previous calculation
        Math.abs( app.cursor[oppositeAxis] - origin[oppositeAxis] ) +

        // add the operation to be performed ( movement of cursor, 1 or -1 )
        operation

        // if the sum of the x, y and current operation are greater then the allowed
        // movement, then make "app.cursor[axis]" equal to itself (dont move) , 
        // otherwise make "app.cursor[axis]" equal to itself plus the operation ( move )
    ) > operation ? app.cursor[axis] : app.cursor[axis] + operation;
}

但是，无论如何我都不会在分配到自我的长线上这样做，为了清晰和易于调试，我会将其分解，并且只使用{{ 1}}：

所以：

if

旁注：你的代码也是The Horror of Implicit Globals的牺牲品，因为你没有声明你的var makecursor = function (axis, operation) { var oppositeAxis = axis === 'y' ? 'x' : 'y'; var movement = // calculate the difference between the current cursor location and the origin Math.abs( app.cursor[axis] - origin[axis] ) + // calculate the difference between the opposite axis and // the origin and add it to the previous calculation Math.abs( app.cursor[oppositeAxis] - origin[oppositeAxis] ) + // add the operation to be performed ( movement of cursor, 1 or -1 ) operation; // If the sum of the x, y and current operation are less than or equal // to the allowed movement, add the operation to `app.cursor[axis]` if (movement <= origin.movement) { app.cursor[axis] += operation; } }变量（以后也有使用它的拼写错误）。我修正了拼写错误并通过在上面添加oppositeAxis来修复隐含的全局。

Answer 2

我想通了，我没有正确地考虑操作，我需要将操作添加到我正在移动的轴上，所以语句

    Math.abs( app.cursor[axis] - origin[axis] ) + 

    // calculate the difference between the opposite axis and
    // the origin and add it to the previous calculation

    Math.abs( app.cursor[oppositeAxis] - origin[oppositeAxis] ) +

    // add the operation to be performed ( movement of cursor, 1 or -1 )
    operation;

应该是这样的：

// add operation to curser location to account for movement
Math.abs(( app.curser[axis] + operation ) - origin[axis] ) + 

// instead of the adding operation at the end
Math.abs( (app.curser[oppositeAxis]) - origin[oppositeAxis] );

javascript逻辑返回奇怪的结果

2 个答案: