javascript 存储在变量中时数组长度未定义
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Array length is undefined when stored in variable
提问by Peter Piper
In the following w3schools example- why does this return 3
在以下w3schools 示例中- 为什么返回 3
<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<script>
var cars = [
"Saab",
"Volvo",
"BMW"
];
document.getElementById("demo").innerHTML = cars.length; //returns 3
</script>
</body>
</html>
and when I try to store cars.length in a variable it returns undefined?
当我尝试将 cars.length 存储在变量中时，它返回未定义？
var test = cars.lenght;
document.getElementById("demo").innerHTML = test; // returns undefined
回答by Branko Sego
You have spelling mistake
你有拼写错误
var test = cars.length;
回答by Mark Eriksson
cars.lenght
???
？？？
"lenght" != "length"
“长度”！=“长度”
回答by Lucky
Typo mistake. You have undefined property (lenght) to access the length property of your array. You should instead use
打字错误。您有未定义的属性 ( lenght) 来访问数组的长度属性。你应该改用
cars.length
cars.length
which gives you the length of the array cars - 3. So var test will have 3 assigned to it.
这为您提供了数组汽车的长度 - 3。因此 var test 将分配给它 3。
回答by Malik Naik
Obviously, cars.lengthreturns 3because we are trying to get the length of array.
显然，cars.length返回3是因为我们试图获取数组的长度。
function myFunction() {
var index;
var text = "<ul>";
var cars= [
"Saab",
"Volvo",
"BMW"];
for (index = 0; index < cars.length; index++) {
text += "<li>" + cars[index] + "</li>";
}
text += "</ul>";
document.getElementById("demo").innerHTML = text;
}
check forloop in the above example it uses index < cars.length
for在上面的例子中检查循环它使用index < cars.length
Output of above code will be
上面代码的输出将是
- Saab
- Volvo
- BMW
- 萨博
- 沃尔沃
- 宝马
