Question

为什么在将变量乘以2并将值赋给另一个变量时，我得到0？基本上，每次按下按钮时，我都会尝试逐步显示/隐藏块。但是，当我算上++ * 2时它会起作用。

请参阅以下代码以供参考。

＆＃13;

var count = 0,
    num = count * 2;

$('.load').on('click', function() {
   $('.blocks').show();
   $('.blocks').slice(num).hide();
    count++;
});

console.log(num); // num is = to 0

＆＃13;

.load {
    display: block;
    margin: 40px 0 0 0;
}

.blocks {
    width: 30px;
    height: 30px;
    background: #000;
    display: inline-block;
    margin: 5px;
}

＆＃13;

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<button class="load">Load this</button>
<div class="blocks"></div>
<div class="blocks"></div>
<div class="blocks"></div>
<div class="blocks"></div>
<div class="blocks"></div>
<div class="blocks"></div>
<div class="blocks"></div>
<div class="blocks"></div>
<div class="blocks"></div>
<div class="blocks"></div>

＆＃13;

Answer 1

// initial variable initialization
var count = 0,
num = count * 2;

$('.load').on('click', function() {
    $('.blocks').show();
    $('.blocks').slice(num).hide();
    // increment the count value
    count++;
    // re assign a new num value
    num = count * 2;
    console.log(num);
    // num is 0,2,4,6
});

console.log(num); // num is = to 0

Answer 2

使num成为一个简单的函数：

function num() { return count * 2; }

乘以javascript变量

2 个答案: