React Native

Enumerate the Header Fields of an Email

Demonstrates the read-only Chilkat Email.NumHeaderFields property together with GetHeaderFieldName and GetHeaderFieldValue to enumerate every header field. Indexing is zero-based, so fields run from 0 to NumHeaderFields - 1. Repeated header fields (a field name that appears more than once) are counted separately. This example builds a small email and prints each header field.

Background: A header field is a single Name: value line at the top of a MIME message. The same field name can legitimately appear multiple times — for example, a message can carry several Received lines, one added by each mail server it passed through. That is why enumerating by index (rather than looking up by name) matters: it lets you see every occurrence in the order it appears.

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React Native

import { Email } from '@chilkat/react-native'

function chilkatExample() {
  // Demonstrates the read-only Email.NumHeaderFields property and enumerating each
  // header field by zero-based index using GetHeaderFieldName and GetHeaderFieldValue.

  const email = new Email();
  email.subject = 'Header field enumeration';
  email.from = 'mary@example.com';
  email.addTo('Joe', 'joe@example.com');

  const n = email.numHeaderFields;
  console.log(`NumHeaderFields = ${n}`);

  for (let i = 0; i < n; i++) {
    console.log(`${email.getHeaderFieldName(i)}: ${email.getHeaderFieldValue(i)}`);
  }
}