javascript - JS 未显示错误结果已更新

Question

不是 39500 输出，而是 500。有人可以帮助我吗，我希望如果 gw 达到 0，墙上就不应该再有 -500。

我使用了我的代码，但它不起作用。 HTML

<li><b>Infantry: </b><span id="gw">40000</span></li>
<p class="fort"><b>Fort: </b><span id="wall">1000</span></p>
<button class="troops" onclick="send()">SEND TROOPS</button>

JS

function send(){
    var a = document.getElementById('gw').innerHTML;
    var b = 500;
    var c = a-b;

    var label = document.getElementById('wall');
    label.innerHTML = parseInt(label.innerHTML) - b;
    var label = document.getElementById('gw');
    label.innerHTML = parseInt(label.innerHTML) - c;

}

Answer 1

您的主要问题是您正在执行 var c = a-b;，b 是一个数字，但 a 是一个字符串(Element.innerHTML) - 没有对该值执行 parseInt(value, radix)...并且其中还有其他数学减法困惑...

相反:

// Helper function to set to 0 a value lower than 0
function zeroMin(val) {
  return parseInt(val, 10) < 0 ? 0 : val;
}

function send() {

  var EL_gw = document.getElementById('gw'),
    EL_wa = document.getElementById('wall'),
    gw = parseInt(EL_gw.innerHTML, 10),
    wa = parseInt(EL_wa.innerHTML, 10),
    hitVal = 500;

  // Subtract
  gw -= hitVal;
  wa -= hitVal;

  // fix to 0
  gw = zeroMin(gw);
  wa = zeroMin(wa);

  EL_gw.innerHTML = gw;
  EL_wa.innerHTML = wa;

}

<b>Infantry:</b> <span id="gw">40000</span> <br>
<b>Fort:</b> <span id="wall">1000</span> <br>

<button class="troops" onclick="send()">SEND TROOPS</button>

如果您想在任何值达到 0 时停止任何进一步的操作

function send() {

  var EL_gw = document.getElementById('gw'),
      EL_wa = document.getElementById('wall'),
    gw = parseInt(EL_gw.innerHTML, 10),
    wa = parseInt(EL_wa.innerHTML, 10),
    hitVal = 500;

  if (gw <= 0 || wa <= 0) return; // Do nothing if any is <= 0 

  // else...
  gw -= hitVal;
  wa -= hitVal;

  EL_gw.innerHTML = gw;
  EL_wa.innerHTML = wa;
  
}

<b>Infantry:</b> <span id="gw">40000</span>
(will stop decreasing if FORT energy is 0 and vice-versa)<br>
<b>Fort:</b> <span id="wall">1000</span> <br>

<button class="troops" onclick="send()">SEND TROOPS</button>