Global Values

The ECMAScript global value properties have mixed support in SSJS. undefined works exactly as expected and NaN behaves correctly for comparisons (only its string form is lowercase). Infinity is severely broken in the SFMC Jint engine: its sign is inverted in both numeric comparisons and string coercion (Infinity > 0 returns false, String(Infinity) yields -infinity). The ES2020 globalThis is not defined.

Status legend

Icon	Meaning
✅ Works	Available and behaves as expected
⚠️ Partial	Available but with a documented caveat or bug
❌ Missing	Not available (or `undefined`) — use the workaround

Members

Member	ES	Status	Notes
`undefined`	ES3	✅ Works
`NaN`	ES3	⚠️ Partial	`String(NaN)` is lowercase `nan`
`Infinity`	ES3	⚠️ Partial	Sign inverted: `Infinity > 0` is `false`, `String(Infinity)` is `-infinity`
`globalThis`	ES2020	❌ Missing	`undefined` — no global-object reference is exposed

undefined

(ES3) — ✅ Works. The primitive undefined value. typeof undefined is "undefined", an unassigned declared variable is undefined, and String(undefined) is "undefined".

var x;
(typeof x === "undefined");   // true
(undefined === undefined);    // true
String(undefined);            // "undefined"

Show test script

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

/*
 * Chapter: undefined
 *
 * Proves:
 *   1. typeof undefined is "undefined".
 *   2. A declared but unassigned variable holds undefined.
 *   3. undefined === undefined is true; it is not equal to null under ===.
 *   4. String(undefined) is "undefined".
 *   5. undefined is falsy and Boolean(undefined) is false.
 *
 * No deviations from the ECMAScript spec are documented for this global.
 *
 * 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 branch(v) { if (v) { return "truthy"; } return "falsy"; }

/* 1. typeof of the global itself. */
assert("typeof undefined is 'undefined'", String(typeof undefined), "undefined");

/* 2. An unassigned declared variable is undefined. */
var x;
assert("typeof unassigned var is 'undefined'", String(typeof x), "undefined");
assert("unassigned var === undefined", x === undefined, true);

/* 3. Identity and non-equality with null under strict compare. */
assert("undefined === undefined", undefined === undefined, true);
assert("undefined === null is false", undefined === null, false);
assert("undefined == null is true (loose compare)", undefined == null, true);

/* 4. String coercion. */
assert("String(undefined) is 'undefined'", String(undefined), "undefined");
assert("'' + undefined is 'undefined'", "" + undefined, "undefined");

/* 5. Falsiness. */
assert("Boolean(undefined) is false", Boolean(undefined), false);
assert("if(undefined) is falsy", branch(undefined), "falsy");
</script>

NaN

(ES3) — ⚠️ Partial. VerifiedDiffers from docs The not-a-number value. Comparisons behave correctly — NaN === NaN is false, isNaN(NaN) is true. Only its string coercion is lowercase (nan) instead of the spec’s NaN.

(NaN === NaN);    // false
isNaN(NaN);       // true
String(NaN);      // "nan" in SFMC (spec: "NaN")

Differs from standard JavaScript (MDN)

MDN specifies String(NaN) produces "NaN"; the SFMC Jint engine produces the lowercase "nan". Comparison semantics are unaffected.

Show test script

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

/*
 * Chapter: NaN
 *
 * Proves:
 *   1. typeof NaN is "number".
 *   2. NaN === NaN is false (and NaN == NaN is false) — the documented
 *      self-inequality.
 *   3. isNaN(NaN) is true; isNaN of a real number is false.
 *   4. NaN is falsy.
 *   5. DEVIATION marked "DEV": String(NaN) yields the lowercase "nan"
 *      (MDN / ECMAScript specify "NaN").
 *   6. The recommended workaround — test with isNaN(), never with a string
 *      comparison against "NaN".
 *
 * EXPECTED OUTPUT: every line starts with PASS.
 */

function assert(id, actual, expected) {
    Platform.Response.Write((actual === expected ? "PASS " : "FAIL ") + id + " -> [" + actual + "]\n");
}
function branch(v) { if (v) { return "truthy"; } return "falsy"; }

/* 1. NaN is a number. */
assert("typeof NaN is 'number'", String(typeof NaN), "number");

/* 2. NaN is not equal to itself. */
assert("NaN === NaN is false", NaN === NaN, false);
assert("NaN == NaN is false", NaN == NaN, false);
var n = NaN;
assert("var holding NaN !== itself", n !== n, true);

/* 3. isNaN detects it. */
assert("isNaN(NaN) is true", isNaN(NaN), true);
assert("isNaN(1) is false", isNaN(1), false);
assert("isNaN('abc') is true", isNaN("abc"), true);

/* 4. Falsiness. */
assert("Boolean(NaN) is false", Boolean(NaN), false);
assert("if(NaN) is falsy", branch(NaN), "falsy");

/* 5. DEVIATION — lowercase string form. */
assert("DEV String(NaN) is 'nan' (spec: 'NaN')", String(NaN), "nan");
assert("DEV '' + NaN is 'nan' (spec: 'NaN')", "" + NaN, "nan");
assert("DEV String(NaN) !== 'NaN'", String(NaN) === "NaN", false);

/* 6. Workaround — detect with isNaN(), not with a string comparison. */
assert("workaround isNaN(String -> Number('abc')) is true", isNaN(Number("abc")), true);
assert("workaround isNaN(parseInt('abc')) is true", isNaN(parseInt("abc", 10)), true);
</script>

Infinity

(ES3) — ⚠️ Partial. VerifiedDiffers from docs The Infinity global is broken in the SFMC Jint engine. typeof Infinity is "number" and Infinity === (1/0) holds, but its sign is inverted everywhere else: Infinity > 0 returns false, Infinity < 0 returns true, and String(Infinity) yields -infinity. Symmetrically, -Infinity (and -1/0) compares as positive and stringifies to infinity. Even Infinity > 1e308 returns false. Do not rely on Infinity/-Infinity for magnitude comparisons or output — compare against a concrete large numeric literal instead.

typeof Infinity;      // "number"
Infinity > 0;         // false  (BUG — should be true)
Infinity < 0;         // true   (BUG)
String(Infinity);     // "-infinity"  (BUG — sign inverted, lowercase)
String(-Infinity);    // "infinity"   (BUG)
Infinity > 1e308;     // false  (BUG)

Differs from standard JavaScript (MDN)

MDN specifies Infinity is a positive value greater than any finite number and String(Infinity) is "Infinity". The SFMC Jint engine inverts the sign of Infinity/-Infinity in both comparison and string coercion (Infinity > 0 is false, String(Infinity) is "-infinity"), making the global unreliable for magnitude checks and output. Prefer comparing against a concrete numeric literal.

Show test script

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

/*
 * Chapter: Infinity
 *
 * Proves:
 *   1. typeof Infinity is "number" and Infinity === (1/0).
 *   2. DEVIATIONS from the ECMAScript spec, each marked "DEV" — the SFMC Jint
 *      engine INVERTS the sign of Infinity / -Infinity:
 *        - Infinity > 0 is false   (spec: true)
 *        - Infinity < 0 is true    (spec: false)
 *        - Infinity > 1e308 is false (spec: true)
 *        - -Infinity < 0 is false / -Infinity > 0 is true (spec: the reverse)
 *        - String(Infinity) is "-infinity"  (spec: "Infinity")
 *        - String(-Infinity) is "infinity"  (spec: "-Infinity")
 *   3. The same inversion applies to the computed forms 1/0 and -1/0.
 *   4. The recommended workaround: compare against a concrete large numeric
 *      literal instead of Infinity — that comparison behaves correctly.
 *
 * EXPECTED OUTPUT: every line starts with PASS.
 */

function assert(id, actual, expected) {
    Platform.Response.Write((actual === expected ? "PASS " : "FAIL ") + id + " -> [" + actual + "]\n");
}

/* 1. Basic identity — these DO match the spec. */
assert("typeof Infinity is 'number'", String(typeof Infinity), "number");
assert("Infinity === (1/0)", Infinity === 1 / 0, true);
assert("-Infinity === (-1/0)", -Infinity === -1 / 0, true);
assert("Infinity === -Infinity is false", Infinity === -Infinity, false);
assert("isNaN(Infinity) is false", isNaN(Infinity), false);

/* 2. DEVIATION — sign inverted in numeric comparisons. */
assert("DEV Infinity > 0 is false (spec: true)", Infinity > 0, false);
assert("DEV Infinity < 0 is true (spec: false)", Infinity < 0, true);
assert("DEV Infinity > 1e308 is false (spec: true)", Infinity > 1e308, false);
assert("DEV -Infinity > 0 is true (spec: false)", -Infinity > 0, true);
assert("DEV -Infinity < 0 is false (spec: true)", -Infinity < 0, false);

/* 3. Same inversion for the computed forms. */
assert("DEV (1/0) > 0 is false (spec: true)", 1 / 0 > 0, false);
assert("DEV (-1/0) > 0 is true (spec: false)", -1 / 0 > 0, true);

/* 4. DEVIATION — sign inverted (and lowercase) in string coercion. */
assert("DEV String(Infinity) is '-infinity' (spec: 'Infinity')", String(Infinity), "-infinity");
assert("DEV String(-Infinity) is 'infinity' (spec: '-Infinity')", String(-Infinity), "infinity");
assert("DEV '' + Infinity is '-infinity'", "" + Infinity, "-infinity");
assert("DEV String(1/0) is '-infinity'", String(1 / 0), "-infinity");

/* 5. Workaround — compare against a concrete numeric literal. */
assert("workaround 1e308 > 0 is true", 1e308 > 0, true);
assert("workaround 5 > 1e-300 is true", 5 > 1e-300, true);
assert("workaround String(1e308) is not lowercase infinity", String(1e308) === "-infinity", false);
</script>

globalThis

(ES2020) — ❌ Missing. globalThis is not defined in the SFMC engine (typeof globalThis === "undefined"). There is no standard reference to the global object; top-level this is also unusable (referencing this at top scope crashes the CloudPage). Reference the specific globals (Platform, Variable, …) you need directly.

(typeof globalThis === "undefined");   // true — not available

Show test script

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

/*
 * Chapter: globalThis  (ES2020)
 *
 * Proves:
 *   1. globalThis is NOT defined in the SFMC engine —
 *      typeof globalThis === "undefined". MDN specifies globalThis is the
 *      standard reference to the global object in every conforming runtime.
 *   2. Referencing it directly does not yield an object.
 *   3. The recommended alternative works: reference the specific globals you
 *      need (Platform, Variable, ...) directly — they ARE defined.
 *
 * NOTE: top-level `this` is deliberately NOT probed here — referencing it at
 * top scope crashes the CloudPage, so it cannot be asserted.
 *
 * EXPECTED OUTPUT: every line starts with PASS.
 */

function assert(id, actual, expected) {
    Platform.Response.Write((actual === expected ? "PASS " : "FAIL ") + id + " -> [" + actual + "]\n");
}

/* 1 + 2. DEVIATION — the ES2020 global is missing. */
assert("DEV typeof globalThis is 'undefined' (spec: 'object')", String(typeof globalThis), "undefined");
assert("DEV typeof globalThis is not 'object'", String(typeof globalThis) === "object", false);

/* 3. Workaround — the concrete globals are available. Platform is a hosted
 *    .NET object, so its typeof is the Jint-specific "clr", not "object". */
assert("workaround Platform is defined (typeof 'clr')", String(typeof Platform), "clr");
assert("workaround typeof Platform is not 'undefined'", String(typeof Platform) === "undefined", false);
assert("workaround typeof Variable is 'object'", String(typeof Variable), "object");
</script>

Global Values

Status legend

Members

undefined

NaN

Infinity

globalThis

See Also

See Also