下面的for (var attr in arr) {}如果换成是普通的for循环会报
Uncaught TypeError: Cannot read property 'style' of null
而for in却不会这是怎么回事
hashchange();
function hashchange() {
var arr = ["a1","b1"];
for (var key in num) {
if (num.hasOwnProperty(key)) {
arr.push(num[key]["classHash"]);
}
}
var firstHash = window.location.hash.substring(1) || arr.shift();
for (var attr in arr) {
document.querySelector("."+arr[attr]).style.display = "none";
document.querySelector("."+firstHash).style.display = "block";
}
};