javascript - this.getElementById 不是函数

Question

https://jsfiddle.net/r3kfjx6a/

let myForm = document.getElementById('myForm')

myForm.addEventListener('submit', function(e){
  e.preventDefault()  
  console.log( this.getElementById('email') )
})

<form id="myForm">
  <input type="email" id="email" placeholder="email">
  <button type="submit">Send</button>
</form>

为什么我无法从this开始在表单内查询？

Answer 1

this 指的是表单元素。由于getElementById()仅适用于document对象，因此您不能使用getElementById() 在其他元素上。尝试使用 querySelector() 代替:

let myForm = document.getElementById('myForm')

myForm.addEventListener('submit', function(e){
  e.preventDefault()  
  console.log( this.querySelector('#email') )
})

<form id="myForm">
  <input type="email" id="email" placeholder="email">
  <button type="submit">Send</button>
</form>