filterValue — GTM Variable Template for Value

VARIABLES › VALUE

filterValue CORE Value

Direct (.tpl) Apply (.tpl)

Tests a value with a callback function and returns the value if it passes the test, otherwise returns undefined. Useful for conditional value filtering in function chains.

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When to Use This

Value Utilities

Handle edge cases — defaults for undefined/null, type checks, coercion.

Filtering

Select or exclude items from collections based on criteria or predicates.

Comparison

Test equality, containment, and ordering between values.

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Examples

Value passes filter▶ Try

INPUT

Value To Test: 42
Test Function: x => typeof x === 'number'

OUTPUT

42

Value fails filter▶ Try

INPUT

Value To Test: hello
Test Function: x => typeof x === 'number'

OUTPUT

undefined

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GTM Configuration

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filterValue

Read-Only Try Live

Value To Test

💾 The value to test with the callback function.

Supported formats:
  ✓ Any type (string, number, object, array, etc.)

Test Function

Returns the value if it passes a test function, otherwise returns undefined.

*** Value passes filter***
Input: Value To Test: 42
Test Function: x => typeof x === 'number'
↪️ Output: 42

*** Value fails filter***
Input: Value To Test: hello
Test Function: x => typeof x === 'number'
↪️ Output: undefined

Input Setup

Input Function (optional)

⚙️ Optional pre-processing function applied to the value before testing (e.g., normalize format, convert types). Internal transformations will still apply afterward.

Result Handling

Output Function (optional)

⚙️ Optional function to apply to the result before returning it (e.g., x => x * 2 to double the value, x => x || 'default' to provide fallback). Useful for chaining transformations on the output.

Value To Test number

💡 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]

Test Function function

🔗 Result Handling — Chain Variables

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

filterValue()

+ Chain another variable

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Related Variables

Same category: Value

→ NaN → apply → applyChain → emptyArray → emptyObject → emptyObjectArray → emptyString → false → falseTo → falsyTo → getLength → getType → identity → mapTruthiness → not → null → nullTo → parseValue → regexTableLookupAll → regexTableLookupCallback → true → undefinedTo → zero

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Under the Hood

📜 View Implementation Code

/**
 * Tests a single value using a callback function and returns the value if it passes.
 * 
 * @param {*} data.src - The value to test.
 * @param {Function} data.cbk - A function that receives the value and returns true to keep it, false to reject it.
 * @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 testing.
 * 
 * @returns {*|undefined} The original value if the callback returns true, otherwise undefined.
 *
 * @framework ggLowCodeGTMKit
 */
const filterValue = function(value, callback) {
   if (typeof callback !== 'function') {
       return undefined;
   }
   return callback(value) ? value : undefined;
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// filterValue - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const processedValue = applyCast(data.pre, data.src);
return out(filterValue(processedValue, data.cbk));
// ===============================================================================
// filterValue(...) – Apply Mode
// ===============================================================================
/*
return function(value, callback) {
  callback = data.rp1 ? data.cbk : callback;
  return out(filterValue(value, callback));
};
*/

🧪 View Test Scenarios (6 tests)

✅ '[example] Value passes filter'
✅ '[example] Value fails filter'
✅ Value passes test - greater than threshold
✅ Undefined value check - passes
✅ Undefined value check - fails
✅ Invalid callback (not a function)