HTML
JAVASCRIPT var list = document.getElementById("div-1").firstChild.id; document.getElementById("demo").innerHTML = list; 我得到的输出是 Undefined 最佳答案 您必须使用的正确属性是firstElementChild var list = document.getElementById("div-1").firstElementChild.id; document.getElementById("demo").innerHTML = list; https://jsfiddle.net/sureshatta/u2q7jpk0/
JAVASCRIPT
var list = document.getElementById("div-1").firstChild.id; document.getElementById("demo").innerHTML = list;
我得到的输出是
Undefined
var list = document.getElementById("div-1").firstElementChild.id; document.getElementById("demo").innerHTML = list;
https://jsfiddle.net/sureshatta/u2q7jpk0/