Html javascript 错误：函数未定义
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javascript error: function is not defined
提问by MrPaulius
I was trying to find the reason why my code doesnt work, and chrome comes back with this eror: Uncaught ReferenceError: calcMPG is not defined... Can someone spot my mistake ?(desperate)
我试图找出我的代码不起作用的原因，而 chrome 又出现了这个错误：Uncaught ReferenceError: calcMPG is not defined... 有人能发现我的错误吗？（绝望）
<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>
回答by Satyam Koyani
Your declarations are wrong please correct them.
您的声明有误，请更正。
var startMileage = document.calc.startingMileage.value ;
var endMileage = document.calc.endingMileage.value;
var gallUsed = document.calc.gallonsUsed.value;
回答by Jonast92
startMileage
and your other right side references don't mean anything, they are undefined variables.
并且您的其他右侧引用没有任何意义，它们是未定义的变量。
Give your inputs an id and fetch the values from them like this:
为您的输入提供一个 id 并从它们中获取值，如下所示：
var startingMileage = document.getElementById('startingMileage').value;
回答by Marco Godínez
I don't know why you do that, but try this:
我不知道你为什么这样做，但试试这个：
<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>
回答by Dmitry
Check here Fiddle
检查这里小提琴
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;
}
