Javascript变量未添加结果，变量为何充当字符串？

Question

Why error ?

expected results = 1360000

result = 1000000360000

 <script> function hitungJumlah() { var jumlah = document.getElementById("pinjam").value; var lama = document.getElementById("kembalinya").value; var bunga = lama * 12/100; var biaya = document.getElementById("biaya").value = jumlah * bunga; document.getElementById("total").value = jumlah + biaya; } </script> 

Answer 1

Because it's read your data as string use parseInt() function to make your data as Integer

Try with this

parseInt(jumlah) + parseInt(biaya)

Beacuse 1000000 and 360000 act as string . + is also used for concatination in javascript

Answer 2

Because the * operator wont type coerce like + operator. Besides you may not have to use document.getElementById() all the time. You might simply do;

<script>
function hitungJumlah() {
  var  jumlah = Number(pinjam.value),
         lama = Number(kembalinya.value),
        bunga = lama * 12/100;
  biaya.value = jumlah * bunga;
  total.value = jumlah + biaya;
}
</script>

Though parseInt() and Number() have differences. While parseInt("42*10") would result 42, as a number object constructor Number("42*10") would result a NaN .

So be careful playing with them.