javascript - 具有多个逻辑运算符的 If 语句不起作用

Question

<script>
    function calculateAmount(val) {
    var quantity = val;
    if (quantity <= 100 && quantity < 1000){
    var divobj = document.getElementById('discount');
    divobj.value = 4;
    var divobj1 = document.getElementById('yousaved');
    var yousaved = 0.4 * quantity;
    divobj1.value = yousaved;
    }
    }
</script>

<form>
<div class="form-group">
<label for=“quantity”>:</label>
<input type="quantity" class="form-control" id="quantity" aria-describedby="quantityHelp" placeholder="100 to 1000000" onchange="calculateAmount(this.value)" required>
<small id="quantityHelp" class="form-text text-muted">Any amount between 100 to 1000000.</small>
</div>
<div class="form-group">
<label for=“discount”>discount in %:</label>
<input type="discount" readonly class="form-control" id="discount" placeholder="Interest">
</div>
<div class="form-group">
<label for=“yousaved”>Total saving:</label>
<input type="yousaved" readonly class="form-control" id="yousaved" placeholder="Your Savings">
</div>
</form>
</div>

if (quantity <= 100 && quantity < 1000)条件不起作用，唯一接受并计算的值是 100，甚至 var 加法和乘法也不起作用，例如:quantity - quantity * 4/100

Answer 1

根据 HTML 中的文本(数字在 100 到 1000 之间)，脚​​本应为:

<script>
function calculateAmount(val) {
    var quantity = val;
    if (quantity >= 100 && quantity <= 1000){
        var divobj = document.getElementById('discount');
        divobj.value = 4;
        var divobj1 = document.getElementById('yousaved');
        var yousaved = 0.4 * quantity;
        divobj1.value = yousaved;
    }
}
</script>