mergeConcat — GTM Variable Template for Object

VARIABLES › OBJECT

mergeConcat EXTENDED Object

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

Merges two objects, concatenating arrays instead of replacing them.

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When to Use This

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Examples

Arrays concatenated on merge▶ Try

INPUT

Base Object: {name: 'John', tags: ['user', 'active']}
Additional Object: {age: 30, tags: ['premium']}

OUTPUT

John

Non-array properties override▶ Try

INPUT

Base Object: {status: 'pending', priority: 1, count: 5}
Additional Object: {status: 'completed', count: 10}

OUTPUT

completed

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Live Sandbox

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mergeConcat

Read-Only Try Live

Base Object

💾 The base object to merge from.

Supported formats:
  ✓ Object variable: {{myObject}}
  ✓ Object literal

Additional Object

💾 The additional object to merge in. Properties override base object, except arrays which are concatenated.

Supported formats:
  ✓ Object variable: {{anotherObject}}
  ✓ Object literal

Input Setup

Input Function (optional)

⚙️ Optional pre-processing function applied to the base object before merging (e.g., normalize structure, parse JSON).

Result Handling

Output Function (optional)

⚙️ Optional function to apply to the merged object before returning it (e.g., obj => JSON.stringify(obj), obj => Object.freeze(obj)). Useful for chaining transformations on the output.

Base Object object

💡 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]

Additional Object object

🔗 Result Handling — Chain Variables

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

mergeConcat()

+ Chain another variable

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Related Variables

Same category: Object

→ applyFromObject → assignDefaults → assignDefaultsDeep → assignObjects → assignObjectsFromPairs → entries → getKeys → getValue → getValueByPath → has → hasKeyEqualTo → hasNested → mergeConcatDeep → omit → pick → pickNested → set → toObjectPairs → values → zipObject → ⚡ OBJECT › From Arrays → ⚡ OBJECT › Smart → ⚡ OBJECT › Transformer (Advanced)

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Under the Hood

📜 View Implementation Code

/**
 * Shallow merges two objects, concatenating arrays instead of replacing them.
 *
 * @param {Object} data.src - The base object to merge from.
 * @param {Object} data.add - The additional object to merge in.
 * @param {Function|string} [data.out] - Optional output handler.
 *
 * Direct-mode specific parameters:
 * @param {Function} [data.pre] - Optional pre-processor function.
 *
 * @returns {Object} A new object with merged properties. Arrays are concatenated, nested objects are replaced.
 *
 * @framework ggLowCodeGTMKit
 */
const getType = require('getType');

const mergeConcat = function(baseObject, additionalObject) {
    const mergedObject = {};

    if (!baseObject || typeof baseObject !== 'object') {
        return additionalObject || {};
    }

    if (!additionalObject || typeof additionalObject !== 'object') {
        return baseObject;
    }

    for (let key in baseObject) {
        if (baseObject.hasOwnProperty(key)) {
            if (getType(baseObject[key]) === 'array' && getType(additionalObject[key]) === 'array') {
                mergedObject[key] = baseObject[key].concat(additionalObject[key]);
            } else if (additionalObject[key] !== undefined) {
                mergedObject[key] = additionalObject[key];
            } else {
                mergedObject[key] = baseObject[key];
            }
        }
    }

    for (let key in additionalObject) {
        if (additionalObject.hasOwnProperty(key) && baseObject[key] === undefined) {
            mergedObject[key] = additionalObject[key];
        }
    }

    return mergedObject;
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// mergeConcat- Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(mergeConcat(value, data.add));
// ===============================================================================
// mergeConcat(...) – Apply Mode
// ===============================================================================
/*
return function(baseObject, additionalObject) {
   additionalObject = data.rp1 ? additionalObject : data.add;
   return out(mergeConcat(baseObject, additionalObject));
};
*/

🧪 View Test Scenarios (5 tests)

✅ '[example] Arrays concatenated on merge'
✅ '[example] Non-array properties override'
✅ Test adding new properties
✅ Test empty additional object
✅ Test array with one empty array