javascript - 错误 : TypeError: undefined is not an object in Java Script

Question

我是 javascript 的新手，我正在试验一些数据来了解数组。不幸的是，我收到的错误是

" Error: TypeError: undefined is not an object in Java Script(evaluating 'dateArray[count] = dateInput[i]')"

我做错了什么？

var dateInput = ["18-Sep-2018", "19-Sep-2018", "20-Sep-2018", "21-Sep-2018", "22-Sep-2018"];
var msInput = [86.69, 86.69, 86.76, 86.86, 86.97];
var hsdInput = [79.58, 79.58, 79.58, 79.58, 79.58];
var startDate, endDate, count;
var dateArray, msArray, hsdArray = new Array();
count = 0;
startDate = "18-Sep-2018";
endDate = "21-Sep-2018";

function createArray() {
    for (i = 0; i < dateInput.length; i = i + 1) {
        if (dateInput[i] >= startDate && dateInput[i] <= endDate) {
            dateArray[count] = dateInput[i];
            count = count + 1;
        }
    }
}
createArray();
console.log(msArray);

Answer 1

你应该这样写:

var dateArray = [], msArray = [], hsdArray = [];

因为在 var dateArray, msArray, hsdArray = new Array();dateArray 和 msArray 未定义