update.js

'use strict';

var key = 'YOURAPIKEY'
  , SparkPost = require('sparkpost')
  , client = new SparkPost(key)
  , updateOpts = {
    dkim: {
      'private': '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',
      'public': 'MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC+W6scd3XWwvC/hPRksfDYFi3ztgyS9OSqnnjtNQeDdTSD1DRx/xFar2wjmzxp2+SnJ5pspaF77VZveN3P/HVmXZVghr3asoV9WBx/uW1nDIUxU35L4juXiTwsMAbgMyh3NqIKTNKyMDy4P8vpEhtH1iv/BrwMdBjHDVCycB8WnwIDAQAB',
      selector: 'hello_selector',
      headers: 'from:to:subject:date'
    }
  };

client.sendingDomains.update('example1.com', updateOpts)
  .then(data => {
    console.log('Congrats you can use our client library!');
    console.log(data);
  })
  .catch(err => {
    console.log('Whoops! Something went wrong');
    console.log(err);
  });

// Using a callback
client.sendingDomains.update('example1.com', updateOpts, function(err, data) {
  if (err) {
    console.log('Whoops! Something went wrong');
    console.log(err);
  } else {
    console.log('Congrats you can use our client library!');
    console.log(data);
  }
});