javascript錯誤：函數未定義

我試圖找到我的代碼不工作的原因，並且chrome返回了這個錯誤：未捕獲的ReferenceError：calcMPG未定義... 有人能發現我的錯誤嗎？絕望）javascript錯誤：函數未定義

<script type="text/javascript"> 
    function calcMPG() { 
     document.calc.startingMileage.value = startMileage; 
     document.calc.endingMileage.value = endMileage; 
     document.calc.gallonsUsed.value = gallUsed; 
     var MPG = (endMileage - startMileage)/gallUsed; 
     if (isNAN(startMileage) || isNAN(endMileage) || isNAN(gallUsed)) alert('please type in numbers only!'); 
     else document.calc.milesPerGalon.value = MPG; 
    } 
</script> 

<form name="calc">Starting mileage: 
    <input type="text" value="0" name="startingMileage" onchange="calcMPG()"> 
    <br>Ending mileage: 
    <input type="text" value="0" name="endingMileage" onchange="calcMPG()"> 
    <br>Gallons used: 
    <input type="text" value="0" name="gallonsUsed" onchange="calcMPG()"> 
    <br>Miles per galon: 
    <input type="text" value="0" name="milesPerGalon"> 
</form>

來源

2013-09-01 MrPaulius

startMileage是不確定的。請填寫完整代碼。 – Dmitry

當我運行這個時，我得到錯誤「未捕獲的ReferenceError：startMileage未定義」，而不是您指定的calcMPG。 –

什麼是'startMileage'，'endMileage'和'gallUsed'？ –

你的聲明是錯了，請糾正。

var startMileage = document.calc.startingMileage.value ; 
var endMileage = document.calc.endingMileage.value; 
var gallUsed = document.calc.gallonsUsed.value;

來源

2013-09-01 18:02:41

startMileage

和你的另一右側引用並不意味着什麼，他們是不確定的變量。

給您輸入ID，並獲取從他們的價值觀是這樣的：

var startingMileage = document.getElementById('startingMileage').value;

來源

2013-09-01 18:01:06 Jonast92

應該是'document.getElementById（'startingMileage'）。value;' –

@PatrickEvans是的，正確的，我在那裏匆匆忙忙。更新。 – Jonast92

我不知道你爲什麼這樣做，但試試這個：

<script type="text/javascript"> 
    function calcMPG(){ 
    var startMileage = document.calc.startingMileage.value, 
     endMileage = document.calc.endingMileage.value, 
     gallUsed  = document.calc.gallonsUsed.value, 
     MPG   = (endMileage - startMileage)/gallUsed; 

     if(isNaN(startMileage) || isNaN(endMileage) || isNaN(gallUsed)){ 
     alert('please type in numbers only!'); 
     } else { 
     document.calc.milesPerGalon.value = MPG; 
     } 
    } 
</script> 
<form name="calc"> 
    Starting mileage:<input type="text" value="0" name="startingMileage" onchange="calcMPG()"><br> 
    Ending mileage:<input type="text" value="0" name="endingMileage" onchange="calcMPG()"><br> 
    Gallons used:<input type="text" value="0" name="gallonsUsed" onchange="calcMPG()"><br> 
    Miles per galon:<input type="text" value="0" name="milesPerGalon"> 
</form>

來源

2013-09-01 18:04:12

入住這裏Fiddle

function calcMPG(){ 
     var startMileage = document.calc.startingMileage.value; 
     var endMileage = document.calc.endingMileage.value; 
     var gallUsed = document.calc.gallonsUsed.value; 

     var MPG = (endMileage - startMileage)/gallUsed; 

     if(isNaN(startMileage) || isNaN(endMileage) || isNaN(gallUsed)) 
      alert('please type in numbers only!'); 
     else 
      document.calc.milesPerGalon.value = MPG; 
    }

來源

2013-09-01 18:08:41 Dmitry

javascript錯誤：函數未定義

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