使用javascript中的document.querySelector在数组中获取值时错误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

我猜对非伪造值（元素与选择器匹配 ）的基本检查是可行的方法：

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

Answer 2

没有与数组中的选择器之一匹配的元素。 在附加事件之前，请执行简单的检查以确保其未定义。

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);
    }
}