javascript - 在javascript中使用document.querySelector获取数组中的值时出现错误NULL？

Question

object = ["a","input","textarea","select","img","#content",".view"];
for (var i = 0; i < oj.length; i++) {
    var resources = document.querySelector(object[i]);
    resources.addEventListener('mouseover', function(){alert("test");}, false);
}

错误TypeError: resources is null，如何解决？

Answer 1

我猜对非虚假值（元素匹配选择器）的基本检查是要走的路：

if (resources) {
    resources.addEventListener("mouseover", function() { ... }, false);
}

Answer 2

没有与您的数组中的选择器之一匹配的元素。在附加事件之前，做一个简单的检查以确保它不是未定义的。

var object = ["a","input","textarea","select","img","#content",".view"];
for (var i = 0; i < oj.length; i++) {
    var resources = document.querySelector(object[i]);
    if(resources){
    resources.addEventListener('mouseover', function(){alert("test");}, false);
    }
}