truncate — GTM Variable Template for String

VARIABLES › STRING

truncate CORE String

Direct (.tpl) Apply (.tpl)

Truncates a string if it is longer than the specified maximum length. The last characters are replaced with the omission string (default ...).

---

When to Use This

String Manipulation

Transform, clean, and normalize text data for consistent downstream processing.

---

Examples

Truncate with ellipsis▶ Try

INPUT

String To Truncate: hello world
Max Length: 8
Use Custom Omission: false
Custom Omission:

OUTPUT

hello...

Short string unchanged▶ Try

INPUT

String To Truncate: hello
Max Length: 10
Use Custom Omission: false
Custom Omission:

OUTPUT

hello

---

GTM Configuration

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

truncate

Read-Only Try Live

String To Truncate

💾 The string to truncate.

Supported formats:
  ✓ String

Max Length

💾 The maximum length the string can be before truncation.

Supported formats:
  ✓ Number

Use Custom Omission

💾 Flag to determine if custom omission should be used instead of default '...'.

Supported formats:
  ✓ Boolean

Custom Omission

💾 The custom omission string to append to the truncated string.

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.

String To Truncate 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]

Max Length number

Use Custom Omission

Custom Omission string

🔗 Result Handling — Chain Variables

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

truncate()

+ Chain another variable

---

Related Variables

Same category: String

→ assignParamsToString → charAt → concatenateValues → countWordsInString → endsWith → extract → extractFirstSegment → extractNumber → fromBase64 → indexOf → left → matchAll → matchRegex → omitParamsFromString → padEnd → padStart → pickParamsFromString → replaceAll → replaceAllWithRegex → replaceFirst → right → safeSplit → sanitizeTextAndRemoveHtml → sanitizeTextLite → search → slice → split → startsWith → test → toBase64 → toCamelCase → toJsonString → toKebabCase → toLocaleLowerCase → toLocaleUpperCase → toLowerCase → toNumber → toSnakeCase → toStartCase → toString → toStringRepresentation → toUpperCase → toUpperFirst → trim → trimEnd → trimStart

---

Under the Hood

📜 View Implementation Code

/**
 * Truncates a string if it is longer than the specified maximum length.
 * The last characters of the truncated string are replaced with the omission string (default is "...").
 *
 * @param {string} data.src - The string to truncate.
 * @param {number} data.max - The maximum length the string can be before truncation.
 * @param {boolean} data.add - Flag to determine if custom omission should be used.
 * @param {string} data.chr - The custom omission string to append to the truncated string.
 * @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 truncating.
 * 
 * @returns {string} The truncated string with the omission string appended, or the original string if it is shorter than the maximum length.
 *
 * @framework ggLowCodeGTMKit
 */
const truncate = function(string, maxLength, addCustomOmission, customChars) {
    const omission = addCustomOmission ? customChars : "...";
    if (typeof string !== 'string' || string.length <= maxLength) {
        return string; 
    }
    return string.slice(0, maxLength - omission.length) + omission;
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// truncate - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(truncate(value, data.max, data.add, data.chr));
// ===============================================================================
// truncate(...) – Apply Mode
// ===============================================================================
/*
return function(value, maxLength, addCustomOmission, customChars) {
   maxLength = data.rp1 ? data.max : maxLength;
   return out(truncate(value, maxLength, data.add, data.chr));
};
*/

🧪 View Test Scenarios (5 tests)

✅ '[example] Truncate with ellipsis'
✅ String longer than max length with custom omission - should truncate with custom chars
✅ '[example] Short string unchanged'
✅ String equal to max length - should return unchanged
✅ Non-string input - should return unchanged