使用javascript中的document.querySelector在數組中獲取值時錯誤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);
}

錯誤TypeError: resources is null ，如何解決？

Answer 1

我猜對非偽造值（元素與選擇器匹配 ）的基本檢查是可行的方法：

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

Answer 2

沒有與數組中的選擇器之一匹配的元素。 在附加事件之前，請執行簡單的檢查以確保其未定義。

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);
    }
}