assignDefaults — GTM Variable Template for Object

VARIABLES › OBJECT

assignDefaults EXTENDED Object

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

Fills in missing properties from a defaults object. Existing values are preserved.

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When to Use This

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Examples

Fill missing properties▶ Try

INPUT

Value to Process: {name: "John", age: 30}
def: {age: 25, city: "Paris", country: "France"}

OUTPUT

{name: "John", age: 30, city: "Paris", country: "France"}

Existing values preserved▶ Try

INPUT

Value to Process: {name: "Alice", age: 40, city: "London"}
def: {name: "Bob", age: 25, city: "Paris"}

OUTPUT

{name: "Alice", age: 40, city: "London"}

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Live Sandbox

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assignDefaults

Read-Only Try Live

Source Object

💾 The base object with initial values.

Default Values

💾 An object containing default values to assign where undefined.

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.

Source Object 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]

Default Values string

🔗 Result Handling — Chain Variables

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

assignDefaults()

+ Chain another variable

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Related Variables

Same category: Object

→ applyFromObject → assignDefaultsDeep → assignObjects → assignObjectsFromPairs → entries → getKeys → getValue → getValueByPath → has → hasKeyEqualTo → hasNested → mergeConcat → 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

/**
 * Assigns default values from the second object to the first.
 *
 * @param {Object} data.src - The base object with initial values.
 * @param {Object} data.def - An object containing default values.
 * @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 merging.
 *
 * @returns {Object} A new object with default values assigned where needed.
 *
 * @framework ggLowCodeGTMKit
 */
const getType = require('getType');

const assignDefaults = function(sourceObject, defaultsObject) {
    const result = {};
    if (getType(sourceObject) === 'object') {
        for (let key in sourceObject) {
            result[key] = sourceObject[key];
        }
    }
    if (getType(defaultsObject) === 'object') {
        for (let key in defaultsObject) {
            if (result[key] === undefined) {
                result[key] = defaultsObject[key];
            }
        }
    }
    return result;
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// assignDefaults - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(assignDefaults(value, data.def));
// ===============================================================================
// assignDefaults(...) – Apply Mode
// ===============================================================================
/*
return function(value, defaultsObject) {
   defaultsObject = data.rp1 ? defaultsObject : data.def;
   return out(assignDefaults(value, defaultsObject));
};
*/

🧪 View Test Scenarios (5 tests)

✅ '[example] Fill missing properties'
✅ Empty base object - returns all defaults
✅ '[example] Existing values preserved'
✅ Non-object source - returns only defaults
✅ Both non-objects - returns empty object