(Node.js) Using Replace Patterns in Email

See more Email Object Examples

Demonstrates how to use the replace patterns (mail-merge) feature in Chilkat MailMan.

Install Chilkat for Node.js and Electron using npm at

Chilkat npm packages for Node.js
Chilkat npm packages for Electron
on Windows, Linux, MacOSX, and ARM

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    var success;

    // ---------------------------------------------------------------------
    // Create an email template for sending.
    var emailTemplate = new chilkat.Email();

    // We're going to replace "FIRST_NAME" with an actual name.
    // We arbitrarily chose "FIRST_NAME".  We can choose anything, such as "CUSTOMER_NAME" or "THE_RECIPIENT_NAME"...
    emailTemplate.Subject = "Hello FIRST_NAME,";

    emailTemplate.From = "john@example.com";
    emailTemplate.AddTo("FIRST_NAME","RECIPIENT_EMAIL");

    emailTemplate.SetHtmlBody("<html><body><h2>Hello FIRST_NAME,</h2><p>Your order for PRODUCT_NAME has been shipped.</p></body></html>");

    // If the email is saved to a file, we can see what it contains:
    emailTemplate.SaveEml("qa_output/emailTemplate.eml");

    // For example:

    // MIME-Version: 1.0
    // Date: Tue, 26 Apr 2022 07:10:52 -0500
    // Message-ID: <715CF231A9F07B0B9FDB073518CD94138D791866@XYZ>
    // Content-Type: text/html; charset=us-ascii
    // Content-Transfer-Encoding: 7bit
    // X-Priority: 3 (Normal)
    // Subject: Hello FIRST_NAME,
    // From: john@example.com
    // CKX-Bounce-Address: john@example.com
    // To: FIRST_NAME <RECIPIENT_EMAIL>
    // 
    // <html><body><h2>Hello FIRST_NAME,</h2><p>Your order for PRODUCT_NAME has been shipped.</p></body></html>

    // Note: Ignore the CKX-Bounce-Address header.  It is automatically removed by Chilkat prior to sending.
    // All "CKX-" headers are automatically removed prior to sending.

    // ---------------------------------------------------------------------
    // Demonstrate replace patterns by setting and then rendering to MIME.

    var mailman = new chilkat.MailMan();

    emailTemplate.SetReplacePattern("FIRST_NAME","Elon");
    emailTemplate.SetReplacePattern("RECIPIENT_EMAIL","elon.musk@example.com");
    emailTemplate.SetReplacePattern("PRODUCT_NAME","Twitter Corporation");

    // Render to MIME to see what we get.
    // Note: When the MailMan sends an email, it renders the email to MIME and then sends.
    // The rendering process is to do replacements, or possibly sign, encrypt, etc.
    // When MailMan.SendEmail is called, internally the email is rendered, and the rendered email is sent.
    // The equivalent to MailMan.Send email is to call email.RenderToMime followed by MailMan.SendMime.
    var mime = mailman.RenderToMime(emailTemplate);
    console.log(mime);

    // This is the rendered MIME:

    // MIME-Version: 1.0
    // Date: Tue, 26 Apr 2022 07:25:49 -0500
    // Message-ID: <750582BCDC891C67B48CEE2293C08B902C3891E9@XYZ>
    // Content-Type: text/html; charset=us-ascii
    // Content-Transfer-Encoding: 7bit
    // X-Priority: 3 (Normal)
    // Subject: Hello Elon,
    // From: john@example.com
    // To: Elon <elon.musk@example.com>
    // 
    // <html><body><h2>Hello Elon,</h2><p>Your order for Twitter Corporation has been shipped.</p></body></html>

    // Note: When rendering, the Date and Message-ID headers are automatically regenerated.

    // ---------------------------------------------------------------------
    // An application can see what replacement patterns it previously set by calling SetReplacePattern multiple times.
    var count = emailTemplate.NumReplacePatterns;
    console.log("Number of replace patterns: " + count);

    var i = 0;
    while (i < count) {
        // Note: The GetReplaceString method was found to not be working correctly.  It was returning the same value as GetReplacePattern.
        // It is fixed in Chilkat v9.5.0.91
        console.log(emailTemplate.GetReplacePattern(i) + ": " + emailTemplate.GetReplaceString(i));
        i = i+1;
    }

    // Or lookup a replacement pattern by name:
    var name = "FIRST_NAME";
    console.log(name + " = " + emailTemplate.GetReplaceString2(name));

    // Sample output:

    // Number of replace patterns: 3
    // FIRST_NAME: Elon
    // RECIPIENT_EMAIL: elon.musk@example.com
    // PRODUCT_NAME: Twitter Corporation
    // FIRST_NAME = Elon

    // ---------------------------------------------------------------------
    // Finally... demonstrate sending emails using the replacement patterns.
    // 

    // Set our mail server settings..
    mailman.SmtpHost = "smtp.mail.us-west-2.awsapps.com";
    mailman.SmtpSsl = true;
    mailman.SmtpPort = 465;

    mailman.SmtpUsername = "john@example.com";
    mailman.SmtpPassword = "the_password";

    // Imagine we have data in JSON format, and we wish to send the templated email to each recipient...
    // 

    // {
    // 	"mail_merge" : [
    // 		{
    // 			"to": "mary@example.com",
    // 			"name": "Mary",
    // 			"product": "Widget 1" 
    // 		},
    // 		{
    // 			"to": "robert@example.com",
    // 			"name": "Robert",
    // 			"product": "Widget 2"
    // 		}	
    // 		...
    // 	]
    // }

    var json = new chilkat.JsonObject();
    success = json.LoadFile("qa_data/json/mail_merge.json");
    if (success == false) {
        console.log(json.LastErrorText);
        return;
    }

    var emailAddr;
    var firstName;
    var product;

    i = 0;
    count = json.SizeOfArray("mail_merge");
    while (i < count) {
        json.I = i;
        emailAddr = json.StringOf("mail_merge[i].to");
        firstName = json.StringOf("mail_merge[i].name");
        product = json.StringOf("mail_merge[i].product");

        emailTemplate.SetReplacePattern("FIRST_NAME",firstName);
        emailTemplate.SetReplacePattern("RECIPIENT_EMAIL",emailAddr);
        emailTemplate.SetReplacePattern("PRODUCT_NAME",product);

        success = mailman.SendEmail(emailTemplate);
        if (success == false) {
            console.log(mailman.LastErrorText);
            return;
        }

        console.log("Send email to " + emailAddr);

        i = i+1;
    }

    console.log("Success.");

}

chilkatExample();