reverseDateCompactYear1st — GTM Variable Template for Date

VARIABLES › DATE

reverseDateCompactYear1st EXTENDED Date

Direct (.tpl) Apply (.tpl)

Reverse a compact date string from "yyyymmdd" to "ddmmyyyy" format with no separators.

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Examples

Reverse yyyymmdd to ddmmyyyy▶ Try

INPUT

Compact Date String: 20241225

OUTPUT

25122024

Leading zeros handled▶ Try

INPUT

Compact Date String: 20250101

OUTPUT

01012025

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GTM Configuration

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reverseDateCompactYear1st

Read-Only Try Live

Compact Date String

💾 The compact date string with no separators, starting with year (yyyymmdd format).

Supported formats:
  ✓ String

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.

Compact Date String 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]

🔗 Result Handling — Chain Variables

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

reverseDateCompactYear1st()

+ Chain another variable

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Related Variables

Same category: Date

→ calculateDaysDifference → currentTimestamp → getDayIndexFromDateString → getDayName → getDayNameFromDateString → getDayNameShort → getMonthName → getMonthNameShort → reverseDateCompactDay1st → reverseDateSlash → timestampToDayIndex

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Under the Hood

📜 View Implementation Code

/**
* Reverse a compact date string from "yyyymmdd" to "ddmmyyyy".
* 
* @param {string} data.src - The compact date string with no separators, starting with year.
* @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 reversing.
* 
* @returns {string|undefined} The reversed date string, or undefined if the input is invalid.
*
* @framework ggLowCodeGTMKit
*/
const reverseDateCompactYear1st = function(date) {
   if (typeof date !== 'string' || date.length !== 8) { return undefined; }
   const year = date.substring(0, 4);
   const month = date.substring(4, 6);
   const day = date.substring(6, 8);
   return day + month + year;
};

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

// ===============================================================================
// reverseDateCompactYear1st - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(reverseDateCompactYear1st(value));

// ===============================================================================
// reverseDateCompactYear1st() – Apply Mode
// ===============================================================================
/*
return function(value) {
  return out(reverseDateCompactYear1st(value));
};
*/

🧪 View Test Scenarios (3 tests)

✅ '[example] Reverse yyyymmdd to ddmmyyyy'
✅ '[example] Leading zeros handled'
✅ Valid date end of year - reverses correctly