Javascript 计数器没有正确递增

Question

我正在尝试在 javascript 中实现一个计数器，当点击“赞”按钮时它递增，而在点击“不赞”按钮时递减。但是，由于某种原因，用户第一次单击拇指向下按钮时，计数器会增加一次，然后开始正确增加（向下）。有人可以查看我的代码并查看是什么原因造成的吗？代码如下：

<script type="text/javascript">
var counter1 = 0;
</script>

<div class="pastel-vote-block">
  <img class="thumbup" onclick="document.getElementById('tallyone').innerHTML = counter1++" src="img/thumb-up-dark.png" height="32" width="32" alt="thumb up">
  <p class="tally" id="tallyone">0</p>
  <img class="thumbdown" onclick="document.getElementById('tallyone').innerHTML = counter1--" src="img/thumb-down-dark.png" height="32" width="32" alt="thumb down">
</div>

Answer 1

<script type="text/javascript">
var counter1 = 0;
</script>

<div class="pastel-vote-block">
  <img class="thumbup" onclick="document.getElementById('tallyone').innerHTML = ++counter1" src="img/thumb-up-dark.png" height="32" width="32" alt="thumb up">
  <p class="tally" id="tallyone">0</p>
  <img class="thumbdown" onclick="document.getElementById('tallyone').innerHTML = --counter1" src="img/thumb-down-dark.png" height="32" width="32" alt="thumb down">
</div>

OP 错误地使用递增和递减运算符

Answer 2

如果在变量后面加上++运算符，counter1赋值给innerHTML后会自增

尝试使用 ++counter1 和 --counter1，因为这将在运算符赋值之前递增并产生预期的输出。

Answer 3

var a = 10, b;

b = a++; // b will be 10, a will be 11

var a = 10, b;

b = ++a; // b will be 11, a will be 11

Javascript 计数器没有正确递增

Javascript counter not incrementing correctly

html

javascript

integer

increment