calculateDiffRatio — GTM Variable Template for Number

VARIABLES › NUMBER

calculateDiffRatio EXTENDED Number

Direct (.tpl) Apply (.tpl)

Calculates the ratio of the difference between two values. Formula: (value - reference) / value.

---

---

Examples

Margin calculation▶ Try

INPUT

Value: 100
Reference Value: 60

OUTPUT

0.4

Zero base returns undefined▶ Try

INPUT

Value: 0
Reference Value: 60

OUTPUT

undefined

---

GTM Configuration

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

calculateDiffRatio

Read-Only Try Live

Value

💾 The base value to use as the denominator and minuend (e.g., price, original value).

Supported formats:
  ✓ Number: 100
  ✓ Stringified Number: "100"
  ✓ Variable: {{price}}

Reference Value

💾 The value to subtract from the base value (e.g., cost, sale price).

Supported formats:
  ✓ Number: 60
  ✓ Stringified Number: "60"
  ✓ Variable: {{cost}}

Input Setup

Input Function (optional)

⚙️ Optional pre-processing function applied to the base value before calculating.

Result Handling

Output Function (optional)

⚙️ Optional function to apply to the result before returning it (e.g., x => x * 100 to convert to percentage, x => (x * 100).toFixed(2) for formatted percentage).

Value 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]

Reference Value number

🔗 Result Handling — Chain Variables

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

calculateDiffRatio()

+ Chain another variable

---

Related Variables

Same category: Number

→ absolute → addValues → calculateRatioPercentage → ceil → clamp → classifyByThreshold → countDigits → divide → floor → max → min → multiply → parseFloatValue → parseIntValue → squareRoot → subtractValues → toFixed → toInteger

---

Under the Hood

📜 View Implementation Code

/**
 * Calculates the ratio of the difference between two values relative to the first value.
 * Formula: (value - reference) / value
 * Useful for margin, discount rate, and other proportional difference calculations.
 *
 * @param {number} data.src - The base value (e.g., price, current value).
 * @param {number} data.ref - The reference value to subtract (e.g., cost, sale price).
 * @param {Function|string} [data.out] - Optional output handler.
 *
 * Direct-mode specific parameters:
 * @param {Function} [data.pre] - Optional pre-processor function.
 *
 * @returns {number|undefined} The ratio (src - ref) / src, or undefined if inputs are invalid.
 *
 * @framework ggLowCodeGTMKit
 */
const makeNumber = require('makeNumber');
const calculateDiffRatio = function(value, reference) {
    const v = makeNumber(value);
    const r = makeNumber(reference);
    if (typeof v !== 'number' || v !== v) return undefined;
    if (typeof r !== 'number' || r !== r) return undefined;
    if (v === 0) return undefined;
    return (v - r) / v;
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// calculateDiffRatio - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(calculateDiffRatio(value, data.ref));
// ===============================================================================
// calculateDiffRatio(...) – Apply Mode
// ===============================================================================
/*
return function(value, reference) {
    reference = data.rp1 ? data.ref : reference;
    return out(calculateDiffRatio(value, reference));
};
*/

🧪 View Test Scenarios (5 tests)

✅ '[example] Margin calculation'
✅ Discount rate
✅ Stringified numbers are converted
✅ '[example] Zero base returns undefined'
✅ Invalid src returns undefined