如何在JavaScript中减去两个东西......？

Question

我正在制作游戏，我需要扣除适量的积分。我的这个陈述不起作用（playerPower）部分。

function checkCol(cell, row){
    var color = map[row][cell];
    console.log(color);
    if (color == "g") {
        alert("Green");
        playerPower -= onGrass - passengerBayPower
    } else if (color == "b") {
        alert("Brown");
        playerPower -= onRock - passengerBayPower
    } else if (color == "w") {
        alert("White");
        playerPower -= onIce - passengerBayPower
    }

- =然后 - ？

是否有问题

Answer 1

您可以通过以下方式简化：

var color = map[row][cell];
var diff = 0;
    console.log(color);
    if (color == "g") {
        alert("Green");
        diff = onGrass - passengerBayPower
    } else if (color == "b") {
        alert("Brown");
        diff = onRock - passengerBayPower
    } else if (color == "w") {
        alert("White");
        diff = onIce - passengerBayPower
    }
    playerPower -= diff;

Answer 2

让我们给你的变量赋一些值。假设playerPower为10，onGrass为2，passengerBayPower为4.您可能希望答案为10 - 2 - 4 = 4，对吧？错...

playerPower -= onGrass - passengerBayPower

对应于......

playerPower = playerPower - (onGrass - passengerBayPower)
            = playerPower - onGrass + passengerBayPower
                                // ^^^ using basic mathematics

这意味着您获得10 - 2 + 4 = 12

要修复，请使用onGrass + passengerBayPower，或完全删除passengerBayPower并将其扔到最后：

playerPower -= passengerBayPower;

因为这对所有情况都很常见。