toUpperFirst — GTM Variable Template for String

VARIABLES › STRING

toUpperFirst CORE String

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

Converts the first character of a string to uppercase and leaves the rest unchanged.

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When to Use This

String Manipulation

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

Type Conversion

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

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Examples

Capitalize first letter▶ Try

INPUT

String To Convert: hello world

OUTPUT

Hello world

Already capitalized▶ Try

INPUT

String To Convert: Hello World

OUTPUT

Hello World

Single character▶ Try

INPUT

String To Convert: a

OUTPUT

A

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Live Sandbox

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

toUpperFirst

Read-Only Try Live

String To Convert

💾 The string to modify.

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 Convert 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]

🔗 Result Handling — Chain Variables

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

toUpperFirst()

+ Chain another variable

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Related Variables

Same category: String

→ charAt → collapseWhitespace → concat → countWordsInString → endsWith → extract → extractFirstSegment → extractNumber → fromBase64 → indexOf → left → matchAll → matchRegex → normalizeEmail → normalizePhone → padEnd → padStart → parseJSON → replaceAll → replaceAllWithRegex → replaceFirst → right → safeSplit → search → slice → slugify → split → startsWith → stripAccents → stripHtml → substringAfter → substringBefore → test → toBase64 → toCamelCase → toJsonString → toKebabCase → toLocaleLowerCase → toLocaleUpperCase → toLowerCase → toNumber → toSnakeCase → toStartCase → toString → toStringRepresentation → toUpperCase → trim → trimEnd → trimStart → truncate

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Under the Hood

📜 View Implementation Code

/**
 * Converts the first character of a string to uppercase and leaves the rest of the string unchanged.
 *
 * @param {string} data.src - The string to modify.
 * @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 {string} The string with the first character converted to uppercase.
 *
 * @framework ggLowCodeGTMKit
 */

const toUpperFirst = function(string) {
    if (typeof string !== 'string' || string.length === 0) {
        return "";
    }
    return string.charAt(0).toUpperCase() + string.slice(1);
};

const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);

// ===============================================================================
// toUpperFirst - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(toUpperFirst(value));
// ===============================================================================
// toUpperFirst() – Apply Mode
// ===============================================================================
/*
return function(value) {
   return out(toUpperFirst(value));
};
*/

🧪 View Test Scenarios (6 tests)

✅ '[example] Capitalize first letter'
✅ '[example] Already capitalized'
✅ All uppercase - should return unchanged
✅ '[example] Single character'
✅ Empty string - should return empty string
✅ Object input - should return empty string