sumPropertyByPath — GTM Variable Template for Items

sumPropertyByPath CORE Items

Direct (.tpl) Apply (.tpl)

Sums a specified numeric property across all objects. Supports nested paths. String numbers are auto-converted.

When to Use This

GA4 Ecommerce

Build and transform ecommerce data structures for GA4 event tracking.

Type Conversion

Safely convert between data types — strings, numbers, booleans, arrays, objects.

Examples

Sum simple property

INPUT

Array of Objects: [
{price: 10},
{price: 20},
{price: 30}
]
Property Path: price

OUTPUT

Sum nested property

INPUT

Array of Objects: [
{product: {price: {amount: 100}}},
{product: {price: {amount: 200}}},
{product: {price: {amount: 150}}}
]
Property Path: product.price.amount

OUTPUT

450

GTM Configuration

This is what you'll see when you open this variable in Google Tag Manager. Hover the icons for details.

sumPropertyByPath

Array of Objects

Property Path

Input Setup

Input Function (optional)

Result Handling

Output Function (optional)

⚙️ Optional function to apply to the sum before returning it (e.g., sum => sum.toFixed(2), sum => sum / 100 for cents to dollars). Useful for chaining transformations on the output.

Array of Objects array

💡 Type any text to see the result update live

🎯 Using special value — click input to type instead

Test with:

Falsy

Truthy

Property Path string

🔗 Result Handling — Chain Variables

sumBy()

Related Variables

Same category: Items

Under the Hood

📜 View Implementation Code

/**
 * Sums a numeric property across all objects in an array, using a path string.
 *
 * @param {Array} data.src - The array of objects.
 * @param {string} data.pth - The path to the numeric value (e.g., "price.amount").
 * @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 {number} The sum of the values found at the specified path. Returns 0 if array is invalid or empty.
 *
 * @framework ggLowCodeGTMKit
 */
const getType = require('getType');
const makeNumber = require('makeNumber');

const getNested = function(obj, path) {
    const parts = path.split('.');
    let current = obj;
    for (let i = 0; i < parts.length; i++) {
        if (current == null || !current.hasOwnProperty(parts[i])) {
            return undefined;
        }
        current = current[parts[i]];
    }
    return current;
};

const sumBy = function(array, path) {
    if (getType(array) !== 'array' || typeof path !== 'string') {
        return 0;
    }
    
    let sum = 0;
    for (let i = 0; i < array.length; i++) {
        const value = makeNumber(getNested(array[i], path));
        if (typeof value === 'number' && value === value) {
            sum += value;
        }
    }
    return sum;
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// sumPropertyByPath - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(sumBy(value, data.pth));
// ===============================================================================
// sumPropertyByPath(...) – Apply Mode
// ===============================================================================
/*
return function(array, path) {
   path = data.rp1 ? data.pth : path;
   return out(sumBy(array, path));
};
*/

🧪 View Test Scenarios (7 tests)

✅ '[example] Sum simple property'
✅ '[example] Sum nested property'
✅ Test with missing property in some objects
✅ Test with string numbers converted to numbers
✅ Test with empty array returns 0
✅ Test with non-numeric values skipped
✅ Test with negative numbers