Embedding SSJS

The `<script runat="server">` Block

SSJS is embedded using an HTML <script> tag with the runat="server" attribute:

<html>
<body>
  <h1>My Page</h1>

  <script runat="server">
  Write("<p>This text comes from SSJS.</p>");
  </script>

  <p>This is regular HTML.</p>
</body>
</html>

The Write() output replaces the script block in the final rendered page. The subscriber sees:

<html>
<body>
  <h1>My Page</h1>

  <p>This text comes from SSJS.</p>

  <p>This is regular HTML.</p>
</body>
</html>

The `language` Attribute

You can optionally specify the language:

<script runat="server" language="JavaScript">
// Explicitly sets JavaScript mode
</script>

This is usually omitted — runat="server" alone is sufficient and implies JavaScript. The language attribute is relevant when a page mixes AMPscript script blocks:

<script runat="server" language="ampscript">
/* AMPscript block */
Set @name = "World"
</script>

<script runat="server" language="JavaScript">
/* SSJS block */
var name = Variable.GetValue("@name");
Write("Hello, " + name);
</script>

Multiple Script Blocks

A single page can have multiple <script runat="server"> blocks. They all share the same execution scope — variables declared in one block are visible in subsequent blocks.

<script runat="server">
// Block 1: Load libraries and declare helpers
Platform.Load("core", "1.1.5");

function formatDate(dateStr) {
    return Platform.Function.FormatDate(dateStr, "MM/DD/YYYY");
}
</script>

<h1>Welcome</h1>

<script runat="server">
// Block 2: Use helpers defined in Block 1
var today = formatDate(Platform.Function.Now());
Write("<p>Today is " + today + "</p>");
</script>

All blocks execute in order before the page is assembled. The output of each block appears at that block’s position in the HTML.

Hoisting Behavior

Function declarations are hoisted within their script block but not across blocks. If you call a function before its block has executed, you’ll get a runtime error.

<script runat="server">
// ❌ This will error — greet() is defined in the next block
Write(greet("World"));
</script>

<script runat="server">
function greet(name) {
    return "Hello, " + name + "!";
}
</script>

Safe pattern: Put all function declarations in the first script block:

<script runat="server">
Platform.Load("core", "1.1.5");

// All function declarations at the top
function greet(name) {
    return "Hello, " + name + "!";
}

function getSubscriberData(sk) {
    return Platform.Function.Lookup("Subscribers", "Email", "SubscriberKey", sk);
}
</script>

<h1>%%=v(@salutation)=%%</h1>

<script runat="server">
// Usage in later blocks is fine
var sk = Platform.Request.GetQueryStringParameter("sk");
Write(greet(getSubscriberData(sk)));
</script>

AMPscript Inside SSJS

AMPscript and SSJS run in the same document and can share data through the Variable namespace:

%%[
  SET @subscriberKey = _subscriberKey
]%%

<script runat="server">
// Read the AMPscript variable in SSJS
var sk = Variable.GetValue("@subscriberKey");

// Write back to AMPscript
var email = Platform.Function.Lookup("Subscribers", "Email", "SubscriberKey", sk);
Variable.SetValue("@email", email);
</script>

<!-- Use the SSJS-set variable in AMPscript -->
<p>Email: %%=v(@email)=%%</p>

Or use Platform.Variable.GetValue / Platform.Variable.SetValue for the same purpose.

Ctrl: Tags (Alternative Syntax)

SFMC also supports older ctrl:field, ctrl:var, and ctrl:eval tags for inline SSJS output. These are legacy and rarely used in new development:

<ctrl:eval>Platform.Function.Now()</ctrl:eval>
<ctrl:var name="myVariable" />
<ctrl:field name="FirstName" />

Stick to <script runat="server"> + Write() for all new work.

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