Getting javascript undefined TypeError

Question

请帮忙...尝试执行下面提到的功能，但 Web 控制台始终显示

TypeError： xml.location.forecast[j] 未定义

我能够在警报中打印值，但由于此错误，代码没有向浏览器提供输出。尝试在不同位置初始化j并使用不同的增量方法。i如何通过此类型错误

Meteogram.prototype.parseYrData = function () {
var meteogram = this,xml = this.xml,pointStart;
if (!xml) {
return this.error();
}
var j;
$.each(xml.location.forecast, function (i,forecast) {
j= Number(i)+1;
var oldto = xml.location.forecast[j]["@attributes"].iso8601;
var mettemp=parseInt(xml.location.forecast[i]["@attributes"].temperature, 10);
var from = xml.location.forecast[i]["@attributes"].iso8601;
var to = xml.location.forecast[j]["@attributes"].iso8601;
from = from.replace(/-/g, '/').replace('T', ' ');
from = Date.parse(from);
to = to.replace(/-/g, '/').replace('T', ' ');
to = Date.parse(to);
if (to > pointStart + 4 * 24 * 36e5) {
return;
}
if (i === 0) {
meteogram.resolution = to - from;
}

meteogram.temperatures.push({
x: from,
y: mettemp,
to: to,
index: i
});
if (i === 0) {
pointStart = (from + to) / 2;
}
});
this.smoothLine(this.temperatures);
this.createChart();
};

Answer 1

您正在尝试访问最后一个元素之后的元素。在继续之前，您可以检查是否有j指向的元素：

Meteogram.prototype.parseYrData = function () {
var meteogram = this,
xml = this.xml,
pointStart;
if (!xml) {
return this.error();
}
var i = 0;
var j;
$.each(xml.location.forecast, function (i, forecast) {
j = Number(i) + 1;
if (!xml.location.forecast[j]) return;
var from = xml.location.forecast[i]["@attributes"].iso8601;
var to = xml.location.forecast[j]["@attributes"].iso8601;
});
};