isDefined — GTM Variable Template for Condition

VARIABLES › CONDITION

isDefined EXTENDED Condition

Direct (.tpl) Apply (.tpl)

Checks if the provided value is not undefined.

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Examples

Defined value returns true▶ Try

INPUT

Value To Check: hello

OUTPUT

true

Undefined returns false▶ Try

INPUT

Value To Check: undefined

OUTPUT

false

Null is defined▶ Try

INPUT

Value To Check: null

OUTPUT

true

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GTM Configuration

This is what you'll see when you open this variable in Google Tag Manager. Hover the icons for details.

isDefined

Read-Only Try Live

Value To Check

💾 The value to check.

Supported formats:
  ✓ All

Input Setup

Input Function (optional)

⚙️ Optional pre-processing function applied to the input before internal logic (e.g., convert object to string, normalize case). Internal transformations such as case handling will still apply afterward.

Result Handling

Output Function (optional)

⚙️ Optional function to apply to the result before returning it (e.g., str => str + ' €', val => val !== undefined for boolean conversion). Useful for chaining transformations on the output.

Value To Check string

💡 Type any text to see the result update live

🎯 Using special value — click input to type instead

Test with:

Falsy undefined null "" empty 0 false NaN

Truthy true 42 "hello" {} empty [] empty {a:1} [1,2,3]

🔗 Result Handling — Chain Variables

Chain apply-mode variables to the output. Each variable receives the result of the previous one.

isDefined()

+ Chain another variable

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Related Variables

Same category: Condition

→ isArray → isEmpty → isEmptyString → isEqualTo → isFalsy → isFunction → isGreaterThan → isGreaterThanOrEqualTo → isInRange → isInfinity → isInteger → isJSON → isLessThan → isLessThanOrEqualTo → isNaN → isNotArray → isNotEmptyString → isNotFunction → isNotJSON → isNotNaN → isNotNull → isNotNumber → isNotObject → isNotString → isNotURL → isNull → isNumber → isObject → isPrimitive → isSHA256 → isString → isStringifiedNumber → isTruthy → isURL → isUndefined → isUnixTimestamp → isUnixTimestampMilliseconds → isUnixTimestampSeconds → isValidNumber

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Under the Hood

📜 View Implementation Code

/**
 * Checks if the provided value is not undefined.
 * 
 * @param {any} data.src - The value to check.
 * @param {Function|string} [data.out] - Optional output handler: function to transform result or string with format.
 *
 * Direct-mode specific parameters:
 * @param {Function} [data.pre] - Optional pre-processor function to transform `src` before checking.
 * 
 * @returns {boolean} True if value is not undefined, false otherwise.
 *
 * @framework ggLowCodeGTMKit
 */
const isDefined = function(value) {
	return value !== undefined;
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// isDefined - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(isDefined(value));
// ===============================================================================
// isDefined() – Apply Mode
// ===============================================================================
/*
return function(value) {
   return out(isDefined(value));
};
*/

🧪 View Test Scenarios (5 tests)

✅ '[example] Defined value returns true'
✅ '[example] Undefined returns false'
✅ '[example] Null is defined'
✅ Zero - should return true
✅ Empty string - should return true