我的求和函数错误，什么也没显示

Question

这是我的javascript代码 我使用总计来计算磁盘，然后我使用总计，磁盘和bayar来计算kembali。

<script type="text/javascript">    
function sum() {
var total = document.getElementById('txtTotal').value;
if (total >= 75000) {
var diskon = parseInt(total) * 0.15;
document.getElementById('txtDiskon').value = diskon;
} else if (total >= 50000 & <=74999) {
var diskon = parseInt(total) * 0.10;
document.getElementById('txtDiskon').value = diskon;
} 
else if (total >= 25000 & <=49000) {
var diskon = parseInt(total) * 0.05;
document.getElementById('txtDiskon').value = diskon;
} 
else if (total >= 0 & <=24999) {
var diskon = 0;
document.getElementById('txtDiskon').value = diskon;
}
var bayar = document.getElementById('txtBayar').value;
var kembali = parseInt(bayar) - (parseInt(total) - parseInt(diskon));
if (!isNaN(kembali)) {
document.getElementById('txtKembali').value = kembali;
}
</script>

这是我的 html 代码

<input name="total" id="txtTotal" onkeyup="sum();" type="text"/>
<input name="diskon" id="txtDiskon" onkeyup="sum();" type="text" />
<input name="bayar" id="txtBayar" onkeyup="sum(); "type="text" />
<input name="kembali" id="txtKembali" type="text"/>

问题是当我使"else if"我的javascript代码没有显示"diskon"并且没有更多错误时。现在我不知道错误在哪里，请帮我修复它

Answer 1

为其他条件更新您的condition total >= 50000 && total <=74999 rather than total >=50000 & <= 74999.相同。查看 [&& 运算符][1]

function sum() {
var total = document.getElementById('txtTotal').value;
if (total >= 75000) {
var diskon = parseInt(total) * 0.15;
document.getElementById('txtDiskon').value = diskon;
} else if (total >= 50000 && total <=74999) {
var diskon = parseInt(total) * 0.10;
document.getElementById('txtDiskon').value = diskon;
} 
else if (total >= 25000 && total <=49000) {
var diskon = parseInt(total) * 0.05;
document.getElementById('txtDiskon').value = diskon;
} 
else if (total >= 0 && total <=24999) {
var diskon = 0;
document.getElementById('txtDiskon').value = diskon;
}
var bayar = document.getElementById('txtBayar').value;
var kembali = parseInt(bayar) - (parseInt(total) - parseInt(diskon));
if (!isNaN(kembali)) {
document.getElementById('txtKembali').value = kembali;
}
}

<input name="total" id="txtTotal" onkeyup="sum()" type="text">
<input name="diskon" id="txtDiskon" onkeyup="sum()" type="text" >
<input name="bayar" id="txtBayar" onkeyup="sum()" type="text" >
<input name="kembali" id="txtKembali" type="text">

[1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_Operators#Logical_AND