apply — GTM Variable Template for Value

VARIABLES › VALUE

apply CORE Value

Direct (.tpl)

Applies a function to a value and returns the result.

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When to Use This

Value Utilities

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

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Examples

Apply function to number▶ Try

INPUT

Input Value: 10
Function: x => x * 2

OUTPUT

20

Invalid function returns undefined▶ Try

INPUT

Input Value: 42
Function: not a function

OUTPUT

undefined

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GTM Configuration

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apply

Read-Only Try Live

Input Value

💾 The value that will be passed to the function.

Supported formats:
  ✓ Any

Function

⚙️ The function that will be applied to the input value.

Supported formats:
  ✓ Function

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.

Input Value any

💡 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]

Function function

🔗 Result Handling — Chain Variables

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

apply()

+ Chain another variable

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Related Variables

Same category: Value

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

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Under the Hood

📜 View Implementation Code

/**
* Applies a function to the input value and returns the result.
* 
* @param {*} data.src - The value that will be passed to the function.
* @param {function} data.fnc - The function that will be applied to the input value.
* @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 processing.
* 
* @returns {*} The result of applying the function to the input value, or undefined if the function is not provided or not a valid function.
*
* @framework ggLowCodeGTMKit
*/
const apply = function(input, func) {
  if (typeof func !== 'function') { return undefined; }
  return func(input);
};

const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);

// ===============================================================================
// apply - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const processedInput = applyCast(data.pre, data.src);
return out(apply(processedInput, data.fnc));

🧪 View Test Scenarios (5 tests)

✅ '[example] Apply function to number'
✅ Valid function applied to string - returns transformed string
✅ Valid function applied to array - returns array length
✅ '[example] Invalid function returns undefined'
✅ Undefined function - returns undefined