if (document.querySelector("#name") !== null) { alert("The element exists"); } else { alert("The element does not exist"); } 在JSFiddle 中编辑 不像querySelector() 方法, querySelectorAll() 返回一个 NodeList 的所有匹配元素。自从 NodeList 是一个对象,你可以检查它的长度属性来检查返回...
其实判断一个元素是否存在,用getElementById()(或其他选择元素的方法)再配合是否为null来判断,或用jQuery获取对象并判断其length,简单又直接。 但如果想判断一个元素是否在当前实时可见的dom中,那就用node.contains(othernode)方法。 参考: 1,How to check if element exists in the visible DOM? 2,What does j...
title Check Event Listener Journey section Event Binding Click_Button(Click the button) --> Check_Listener{Check if listener exists} section Check Result Check_Listener --> |Yes| Output_Result[Output 'true'] Check_Listener --> |No| Output_Result[Output 'false'] 通过以上内容的介绍,相信您已经...
AI代码解释 constarr=[1,2,3,4,5];// Check if there is the number 3 in the arrayarr.include(3);// trueif(arr.include(3)){...}// ... Equivalent to the previous writing of indexOfarr.indexOf(3);// 2 (return its array position)// If you want to write it in the if, you...
This checks if 'name' and 'email' properties exist in the person object. The first check returns true as 'name' exists, while 'email' returns false. The property name must be specified as a string. $ node main.js true false Checking array indices...
In JavaScript, you can use thecontains()method provided by theclassListobject to check if any element contains a specific CSS class. This method returnstrueif the class exists. Otherwise,falseis returned. Let us say we have the following HTML element: ...
Note that such a token always exists: if a comment appears at the end of a file, its following token is an EOFToken. As an example of a query using only lexical information, consider the following query for finding HTML comments, which are not a standard ECMAScript feature and should be...
如何找到data-element(data-qa)的父属性。我有一个数据属性id,data-qa=productId1,productid2,productid3。(对于网格中的每一行) 对于网格中的每个行号。 如何判断父元素上面是否有kendogridcell? 我不知道kendogridcell是什么,它不是一个类。 let dataQaElements = document.querySelectorAll(`[data-qa]`);...
问无法读取Javascript类中未定义的属性“存储”EN我编写了一个小型的方便类来集中处理我们在应用程序中所...
}// tmp still exists here// => not what we want} 如果要为then块引入新的作用域,可以定义一个函数并立即调用它。这是一种解决方法,模拟块作用域: functionf() {if(condition) { (function() {// open blockvartmp = ...; ... }());// close block} ...