isFalsy — GTM Variable Template for Logic

VARIABLES › LOGIC

isFalsy EXTENDED Logic

Direct (.tpl) Apply (.tpl) Add to GTM

Checks if the provided value is falsy. Falsy values are undefined, null, false, NaN, 0, and '' (empty string).

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When to Use This

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Examples

Empty string is falsy▶ Try

INPUT

Value To Check:

OUTPUT

true

Non-empty string is not falsy▶ Try

INPUT

Value To Check: hello

OUTPUT

false

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Live Sandbox

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isFalsy

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.

isFalsy()

+ Chain another variable

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Related Variables

Same category: Logic

→ isArray → isDefined → isEmpty → isEmptyString → isEqualTo → 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 → 🧩 AND → 🧩 IF (else) → 🧩 IF AND_OR → 🧩 IF ELSE IF (Advanced) → 🧩 IF ELSE IF (Predefined) → 🧩 NOT → 🧩 OR → 🧩 XOR

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Under the Hood

📜 View Implementation Code

/**
 * Checks if the value is falsy.
 *
 * @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 the value is falsy, false otherwise.
 * @framework ggLowCodeGTMKit
 */
const isFalsy = function(value) {
  return !value;
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// isFalsy - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(isFalsy(value));
// ===============================================================================
// isFalsy() – Apply Mode
// ===============================================================================
/*
return function(value) {
   return out(isFalsy(value));
};
*/

🧪 View Test Scenarios (5 tests)

✅ False - should return true
✅ Zero - should return true
✅ '[example] Empty string is falsy'
✅ Null - should return true
✅ '[example] Non-empty string is not falsy'