EndImpressionRegion

Parameters

Name	Type	Required	Description
`closeAll`	string \| boolean \| number	No	When `true`, closes every nested impression region still open

Show test script

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

/*
 * Chapter: Parameters — Platform.Function.EndImpressionRegion([closeAll])
 *
 * Proves:
 *   1. The member resolves on Platform.Function (typeof "clrmethodinfo",
 *      the engine's marker for a host CLR method).
 *   2. The documented 0-argument form is callable and returns a value —
 *      unlike its paired BeginImpressionRegion half, which throws for
 *      every SSJS call shape.
 *   3. The optional closeAll parameter accepts a boolean: both true and
 *      false are accepted and both return null.
 *   4. Non-boolean values in the closeAll position are coerced rather than
 *      rejected — a string and a number are both accepted.
 *   5. null in the closeAll position is NOT accepted: it throws the
 *      engine's overloaded "Unable to retrieve security descriptor for
 *      this frame." error.
 *   6. Arities beyond the documented maximum of 1 (2 and 3 arguments)
 *      throw the same security-descriptor error.
 *
 * SCOPE: run as a CloudPage GET only. Nothing below asserts how the call
 * behaves inside an actual email send.
 *
 * NOT ASSERTED: whether an impression region is actually closed in
 * Marketing Cloud tracking. Impression counts surface in tracking reports
 * after a send is processed, which is not deterministically observable
 * from inside the rendering request, so only the call-level behaviour is
 * asserted.
 *
 * EXPECTED OUTPUT: every line starts with PASS. A FAIL means the runtime no
 * longer matches the documented claim and the page must be revised.
 */

function assert(id, actual, expected) {
    Platform.Response.Write((actual === expected ? "PASS " : "FAIL ") + id + " -> [" + actual + "]\n");
}
function assertThrows(id, fn) {
    var threw = false, msg = "";
    try { fn(); } catch (ex) { threw = true; msg = ex.message; }
    Platform.Response.Write((threw ? "PASS " : "FAIL ") + id + " -> " + (threw ? "threw: " + msg : "did NOT throw") + "\n");
}

/* 1. The member resolves as a host CLR method. */
assert("typeof Platform.Function.EndImpressionRegion is clrmethodinfo", String(typeof Platform.Function.EndImpressionRegion), "clrmethodinfo");

/* 2. The 0-argument form is callable and returns null. */
var r0 = Platform.Function.EndImpressionRegion();
assert("arity 0 returns typeof object", String(typeof r0), "object");
assert("arity 0 returns a genuine null", r0 === null ? "true" : "false", "true");

/* 3. closeAll accepts a boolean in either state. */
var rTrue = Platform.Function.EndImpressionRegion(true);
assert("closeAll = true is accepted and returns null", rTrue === null ? "true" : "false", "true");
var rFalse = Platform.Function.EndImpressionRegion(false);
assert("closeAll = false is accepted and returns null", rFalse === null ? "true" : "false", "true");

/* 4. Non-boolean closeAll values are coerced, not rejected. */
var rStr = Platform.Function.EndImpressionRegion("true");
assert("closeAll = \"true\" (string) is coerced and returns null", rStr === null ? "true" : "false", "true");
var rNum = Platform.Function.EndImpressionRegion(1);
assert("closeAll = 1 (number) is coerced and returns null", rNum === null ? "true" : "false", "true");

/* 5. null in the closeAll position is rejected. */
assertThrows("closeAll = null throws the security-descriptor error", function () {
    return Platform.Function.EndImpressionRegion(null);
});

/* 6. Arities above the documented maximum of 1 throw. */
assertThrows("arity 2 throws (documented maximum is 1)", function () {
    return Platform.Function.EndImpressionRegion(true, true);
});
assertThrows("arity 3 throws (documented maximum is 1)", function () {
    return Platform.Function.EndImpressionRegion(true, true, true);
});
</script>

Differs from official Salesforce docs

The official docs type the return as void, but the runtime always returns a genuine null (typeof “object”, === null) — even when called with no matching BeginImpressionRegion. Scope: measured on CloudPage GET requests only — the behaviour inside a real email send was never exercised and may differ.

Show test script — returns a genuine null, not void

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

/*
 * Differs-from-docs claim: the official Salesforce documentation types the
 * return of EndImpressionRegion as VOID. At runtime the qualified
 * Platform.Function form always returns a genuine JavaScript null.
 *
 * Official docs: EndImpressionRegion([closeAll]) returns void
 * SFMC runtime:  it returns null — typeof "object", === null is true,
 *                === undefined is false
 *
 * Proves every part of the callout:
 *   1. DEV the return is typeof "object", not "undefined" — a void return
 *      would surface as undefined in JavaScript.
 *   2. DEV the return is strictly === null.
 *   3. DEV the return is NOT === undefined, which is what distinguishes a
 *      genuine null from the documented void.
 *   4. The same holds when there is NO matching BeginImpressionRegion —
 *      every call in this script is unmatched, because the paired
 *      BeginImpressionRegion half cannot be invoked from SSJS at all
 *      (see /platform-functions/beginimpressionregion/). The call still
 *      returns null instead of throwing or returning undefined.
 *   5. The closeAll form returns null too, so the deviation is not tied to
 *      a particular arity.
 *   6. CONTRAST: the bare-name Core alias EndImpressionRegion() is a
 *      genuine "function" (not "clrmethodinfo") and returns UNDEFINED —
 *      so the two forms disagree with each other, and only the
 *      Platform.Function form returns null.
 *
 * SCOPE: all of the above was observed on a plain CloudPage GET. No
 * assertion here speaks to what happens during a real email send, which
 * was never exercised and may behave differently.
 *
 * EXPECTED OUTPUT: every line starts with PASS.
 */

function assert(id, actual, expected) {
    Platform.Response.Write((actual === expected ? "PASS " : "FAIL ") + id + " -> [" + actual + "]\n");
}
function assertNoThrow(id, fn) {
    var threw = false, msg = "";
    try { fn(); } catch (ex) { threw = true; msg = ex.message; }
    Platform.Response.Write((threw ? "FAIL " : "PASS ") + id + " -> " + (threw ? "threw: " + msg : "did not throw") + "\n");
}

/* 4. Establish that no matching BeginImpressionRegion can exist in SSJS:
   the paired half throws for every call shape. */
var beginThrew = false;
try { Platform.Function.BeginImpressionRegion("unmatched-control"); } catch (ex) { beginThrew = true; }
assert("control: no matching Begin is possible from SSJS — the paired half throws", beginThrew ? "true" : "false", "true");

/* 1-3. DEV the unmatched 0-argument call returns a genuine null, not void. */
var r = Platform.Function.EndImpressionRegion();
assert("DEV unmatched call returns typeof object (docs: void)", String(typeof r), "object");
assert("DEV unmatched call returns === null (docs: void)", r === null ? "true" : "false", "true");
assert("DEV unmatched call is NOT === undefined, so it is not void", r === undefined ? "true" : "false", "false");

/* 4. It does not throw despite having nothing to close. */
assertNoThrow("an unmatched EndImpressionRegion does not throw", function () {
    return Platform.Function.EndImpressionRegion();
});

/* 5. The closeAll form deviates identically. */
var rc = Platform.Function.EndImpressionRegion(true);
assert("DEV closeAll form returns typeof object (docs: void)", String(typeof rc), "object");
assert("DEV closeAll form returns === null (docs: void)", rc === null ? "true" : "false", "true");
assert("DEV closeAll form is NOT === undefined", rc === undefined ? "true" : "false", "false");

/* 6. CONTRAST — the bare-name Core alias returns undefined instead. */
assert("contrast: typeof the bare-name Core alias is function", String(typeof EndImpressionRegion), "function");
var b = EndImpressionRegion();
assert("contrast: the bare-name Core alias returns typeof undefined", String(typeof b), "undefined");
assert("contrast: the bare-name Core alias is === undefined, not null", b === undefined ? "true" : "false", "true");
assert("contrast: the bare-name Core alias is NOT === null", b === null ? "true" : "false", "false");
</script>

⚠ Scope of the evidence — CloudPage only. Every observation on this page comes from plain GET requests against a CloudPage. Nothing here was measured inside a real email send. Since impression regions exist primarily to track what a recipient sees in a delivered message, treat the send-time behaviour as untested: it may well differ from what is described here.

Examples

EndImpressionRegion() is callable directly from SSJS, but its paired half is not: every SSJS BeginImpressionRegion() call throws, so the region has to be opened with the AMPscript form via TreatAsContent().

Platform.Function.TreatAsContent('%%[BeginImpressionRegion("sidebar")]%%');
Write(sidebarBlocks);
Platform.Function.EndImpressionRegion();

Platform.Function.TreatAsContent('%%[BeginImpressionRegion("outer")]%%');
Platform.Function.TreatAsContent('%%[BeginImpressionRegion("inner")]%%');
Write(nestedContent);
Platform.Function.EndImpressionRegion(true);