我收到NaN錯誤

Question

我在這個計算器腳本中收到NaN錯誤： 有沒有想法？

這裏是文本格式的全HTML：

https://www.dropbox.com/s/i3u429bn5bjd4i9/orecalculator.txt

<script language="JavaScript"> 

var IDs = [22,17425,17426,1223,17428,17429,1225,17432,17433,1232,17436,17437,1229,17865,17866,21,17440,17441,1231,17444,17445,1226,17448,17449,20,17452,17453,11396,17869,17870,1227,17867,17868,18,17455,17456,1224,17459,17460,1228,17463,17464,19,17466,17467,1230,17470,17471]; 

function calculate(i){ 
    while (i + 1 < IDs.length) { 
     var y=document.getElementById('reward'); 
     var x=document.getElementById(IDs[i]); 
     y.value=parseInt(y.value)+parseInt(x.value); 
     i++; 
    } 
} 
</script> 

Answer 1

我已經運行在控制檯這個代碼，發現下面的輸出

document.getElementById('reward') 
//output <input type=​"text" id=​"reward">​ 
document.getElementById('reward').value 
//"" 
parseInt(document.getElementById('reward').value) 
//NaN 
parseInt("") 
//NaN 

說明

空字符串parseInt函數是NaN

解決方案

使用

Reward: <input type="text" id="reward" value="0"> 

代替

Reward: <input type="text" id="reward"> 

修正：JS代碼

function calculate(i){ 
    while (i + 1 < IDs.length) { 
     var y=document.getElementById('reward'); 
     var x=document.getElementById(IDs[i]); 
     y.value=parseInt(y.value|0)+parseInt(x.value|0); 
     i++; 
    } 
} 

Answer 2

未經檢驗的，但應該是這樣的：

calculate = function (i){ 

    var y = document.getElementById('reward'); 
    var x = 0; 
    while (i + 1 < IDs.length) { 

     var elm = document.getElementById(IDs[i]); 
     x+=parseInt(elm.value||0); 
     i++; 
    } 
    y.value = x; 
}; 

工作小提琴：

http://jsfiddle.net/g30rg3/8ADQX/