我試圖GDPAnn從陣列中找到最后一個值Annual。下面的代碼作業正常。但如果GDPAnn在最后一個值中不可用，則回傳undefined. 例如，我想要10251000來自 array 的 GDPAnn 的值Annual2。
var Annual = [{"Date":1998,"Value":4.5,"GDPAnn":9062800},{"Date":1999,"Value":4.8,"GDPAnn":9631200},{"Date":2000,"Value":4.1,"GDPAnn":10251000},{"Date":2001,"Value":1,"GDPAnn":10581900}]
x = Annual.map((o) => o.GDPAnn).pop();
console.log(x);
var Annual2 = [{"Date":1998,"Value":4.5,"GDPAnn":9062800},{"Date":1999,"Value":4.8,"GDPAnn":9631200},{"Date":2000,"Value":4.1,"GDPAnn":10251000},{"Date":2001,"Value":1}]
y = Annual2.map((o) => o.GDPAnn).pop();
console.log(y);uj5u.com熱心網友回復：
請參閱下面代碼中的注釋 - 使用.filter()
var Annual = [{"Date":1998,"Value":4.5,"GDPAnn":9062800},{"Date":1999,"Value":4.8,"GDPAnn":9631200},{"Date":2000,"Value":4.1,"GDPAnn":10251000},{"Date":2001,"Value":1,"GDPAnn":10581900}]
x = Annual.map((o) => o.GDPAnn).pop();
console.log(x);
var Annual2 = [{"Date":1998,"Value":4.5,"GDPAnn":9062800},{"Date":1999,"Value":4.8,"GDPAnn":9631200},{"Date":2000,"Value":4.1,"GDPAnn":10251000},{"Date":2001,"Value":1}]
// Adding filter here to only include items with the GDPAnn key
y = Annual2.filter((o) => o.GDPAnn).map((o) => o.GDPAnn).pop();
console.log(y);uj5u.com熱心網友回復：
這可能是一個簡單的解決方法
var Annual = [{"Date":1998,"Value":4.5,"GDPAnn":9062800},{"Date":1999,"Value":4.8,"GDPAnn":9631200},{"Date":2000,"Value":4.1,"GDPAnn":10251000},{"Date":2001,"Value":1,"GDPAnn":10581900}]
x = Annual.map((o) => o.GDPAnn).pop();
console.log(x);
var Annual2 = [{"Date":1998,"Value":4.5,"GDPAnn":9062800},{"Date":1999,"Value":4.8,"GDPAnn":9631200},{"Date":2000,"Value":4.1,"GDPAnn":10251000},{"Date":2001,"Value":1}]
y = Annual2.filter(o=> o.GDPAnn).map((o) => o.GDPAnn).pop();
console.log(y);uj5u.com熱心網友回復：
let y = Annual2.reduce((prev, curr) => curr.GDPAnn ? curr : prev).GDPAnn
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標籤：javascript