JavaScript：返回 NAN 的函数
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JavaScript: function returning NAN
提问by Leahcim
I'm working on a codecademy.com lesson with instructions to write the calculateTotal function below. When I click run, it's returning NaN. Anyone know what's wrong with the calculateTotal function as I wrote it that's making it return NaN. Note, I understand that NaN means not a number...
我正在编写 codecademy.com 课程，其中包含编写下面的calculateTotal 函数的说明。当我单击运行时，它返回 NaN。任何人都知道我编写的calculateTotal 函数有什么问题，这使它返回NaN。请注意，我知道 NaN 表示不是数字......
// runner times
var carlos = [9.6,10.6,11.2,10.3,11.5];
var liu = [10.6,11.2,9.4,12.3,10.1];
var timothy = [12.2,11.8,12.5,10.9,11.1];
// declare your function calculateTotal here
var calculateTotal = function(raceTimes){
var totalTime;
for(i = 0; i < raceTimes.length; i++){
totalTime += raceTimes[i];
return totalTime;
}
};
var liuTotal = calculateTotal(liu);
console.log(liuTotal);
Note, many of the people answering this question have said that var totalTime has to be set to "O". However, in the next codecademy lessson, the author writes a function with totalTime not set to anything and it works
请注意，许多回答这个问题的人都说 var totalTime 必须设置为“O”。但是，在接下来的 codecademy 课程中，作者编写了一个 totalTime 未设置为任何内容的函数，并且可以正常工作
var calculateAverage = function (raceTimes) {
var totalTime;
for ( i = 0; i < raceTimes.length; i++ ) {
totalTime = (totalTime || 0) + raceTimes[i];
}
// assign variable averageTime
var averageTime = totalTime / raceTimes.length;
return averageTime;
};
回答by Jamie Treworgy
Two problems:
两个问题：
totalTimeis not defined -- adding something to an undefined results inNaN- You are returning INSIDE your loop.
totalTime未定义——向未定义的结果中添加内容NaN- 您正在循环内部返回。
Fix:
使固定：
var totalTime=0;
for(i = 0; i < raceTimes.length; i++){
totalTime += raceTimes[i];
}
return totalTime;
回答by Richard JP Le Guen
Your totalTimedoesn't have an initial value, so it starts off as undefined. You can't add a number to undefinedand get a number:
您totalTime没有初始值，因此它以undefined. 您无法添加数字undefined并获得数字：
var totalTime; // implicitly initialized to undefined
for(i = 0; i < raceTimes.length; i++){
totalTime += raceTimes[i]; // undefined + raceTimes[i] = NaN
return totalTime;
}
Initialize it to 0.
将其初始化为0.
var totalTime = 0;
回答by 0x499602D2
You haven't initialized totalTimewith a value. So it defaults to undefined. Therefore on each iteration, undefined is being added, yielding NaN.
您尚未totalTime使用值进行初始化。所以它默认为undefined. 因此，在每次迭代中，都会添加 undefined ，从而产生NaN.
