Question

我有这个组件：

export class FileFormComponent {
  _base64: string;

 handleFile($event){
   var input = $event.target;
   var reader = new FileReader();
   reader.onloadend = function() {
     this._base64 = reader.result
   }
   reader.readAsDataURL(input.files[0]);
   console.log(this._base64);
 }
}

问题是console.log(this._base64)日志undefined。 this事件中的onloadend似乎并未引用组件的上下文。如何在_base64 FileReader事件中设置onloadend属性的值。

Answer 1

我会使用箭头功能。这样你就可以使用lexical this（对应于组件实例）：

reader.onloadend() = () => {
  this._base64 = reader.result
}

有关详细信息，请参阅此链接：

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions

Answer 2

我用于这种情况的模式是：

    <?php
if(isset($_POST['email'])) {

    // CHANGE THE TWO LINES BELOW
    $email_to = "name@domain.com";

    $email_subject = "website html form submissions";


    function died($error) {
        // your error code can go here
        echo "We are very sorry, but there were error(s) found with the form you submitted. ";
        echo "These errors appear below.<br /><br />";
        echo $error."<br /><br />";
        echo "Please go back and fix these errors.<br /><br />";
        die();
    }

    // validation expected data exists
    if(!isset($_POST['first_name']) ||
        !isset($_POST['last_name']) ||
        !isset($_POST['email']) ||
        !isset($_POST['telephone']) ||
        !isset($_POST['comments'])) {
        died('We are sorry, but there appears to be a problem with the form you submitted.');       
    }

    $first_name = $_POST['first_name']; // required
    $last_name = $_POST['last_name']; // required
    $email_from = $_POST['email']; // required
    $telephone = $_POST['telephone']; // not required
    $comments = $_POST['comments']; // required

    $error_message = "";
    $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/';
  if(!preg_match($email_exp,$email_from)) {
    $error_message .= 'The Email Address you entered does not appear to be valid.<br />';
  }
    $string_exp = "/^[A-Za-z .'-]+$/";
  if(!preg_match($string_exp,$first_name)) {
    $error_message .= 'The First Name you entered does not appear to be valid.<br />';
  }
  if(!preg_match($string_exp,$last_name)) {
    $error_message .= 'The Last Name you entered does not appear to be valid.<br />';
  }
  if(strlen($comments) < 2) {
    $error_message .= 'The Comments you entered do not appear to be valid.<br />';
  }
  if(strlen($error_message) > 0) {
    died($error_message);
  }
    $email_message = "Form details below.\n\n";

    function clean_string($string) {
      $bad = array("content-type","bcc:","to:","cc:","href");
      return str_replace($bad,"",$string);
    }

    $email_message .= "First Name: ".clean_string($first_name)."\n";
    $email_message .= "Last Name: ".clean_string($last_name)."\n";
    $email_message .= "Email: ".clean_string($email_from)."\n";
    $email_message .= "Telephone: ".clean_string($telephone)."\n";
    $email_message .= "Comments: ".clean_string($comments)."\n";


// create email headers
$headers = 'From: '.$email_from."\r\n".
'Reply-To: '.$email_from."\r\n" .
'X-Mailer: PHP/' . phpversion();
@mail($email_to, $email_subject, $email_message, $headers);  
?>

<!-- place your own success html below -->

Thank you for contacting us. We will be in touch with you very soon.

<?php
}
die();
?>

如何从FileReader事件中设置Component的属性值

2 个答案: