使用占位符（用于输入框）的值作为JS中的条件

Question

(This is all made with HTML and JS) I made this program that takes a decimal number, converts it into binary and gives you the result. The input box that takes the decimal number has a placeholder 'Enter decimal number'. After I made the decimal to binary part functional, I started on making a reverse button that would first change the placeholder to 'Enter binary number'. These are the HTML and JS codes:

 function reverseButton() { if (document.getElementsByClassName('inputBox').placeholder === 'Enter decimal number') { document.getElementsByClassName('inputBox').placeholder='Enter binary number'; } else if (document.getElementsByClassName('inputBox').placeholder === 'Enter binary number') { document.getElementsByClassName('inputBox').placeholder='Enter decimal number'; } } 

 <input type="number" class="inputBox" id="decimalNumber" placeholder="Enter decimal number" min="0" step="0.0001"> <button class="button hoverTurquoise reverse" onclick="reverseButton()">Reverse</button> 

I tried to first set the place holder to nothing (empty '') and then adding the text but I get the same result. If anyone knows what to do, your help would be greatly appreciated.

Answer 1

getElementsByClassName函数返回一个数组，因此您必须将代码转换为这种形式

if (document.getElementsByClassName('inputBox')[0].placeholder === 'Enter decimal number') {