extractHost — GTM Variable Template for URL

VARIABLES › URL

extractHost CORE URL

Direct (.tpl) Apply (.tpl)

Extracts the host (hostname + port) from a URL.

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When to Use This

URL Processing

Parse, build, decode, and manipulate URLs and query parameters.

Extraction

Pull specific values, segments, or patterns from complex data structures.

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Examples

Extract host with port

INPUT

URL: https://example.com:8080/page

OUTPUT

example.com:8080

Extract host without port

INPUT

URL: https://example.com/page

OUTPUT

example.com

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GTM Configuration

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Read-only Preview

extractHost

URL

💾 The URL to extract the host from.

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.

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Related Variables

Same category: URL

→ buildUrlFromParts → completeUrl → decodeUri → decodeUriComponent → encodeURIComponent → encodeUri → extractHash → extractHashParams → extractHostname → extractOrigin → extractPasword → extractPathname → extractPort → extractProtocol → extractSearch → extractSearchParams → extractSegmentByIndex → extractUserName → hasFragment → hasParameterWithValue → hasQueryString → parseUrlComponents → stringToPath

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Under the Hood

📜 View Implementation Code

/**
 * Extracts the host from a given URL.
 *
 * @param {string} data.src - The URL to extract the host from.
 * @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 extracting.
 * 
 * @returns {string|undefined} The host from the URL, or undefined if the input is invalid.
 *
 * @framework ggLowCodeGTMKit
 */

const parseUrl = require('parseUrl');

const extractHost = function(url) {
    const parsed = parseUrl(url);
    return parsed && parsed.host || undefined;
};

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

// ===============================================================================
// extractHost - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(extractHost(value));

// ===============================================================================
// extractHost() – Apply Mode
// ===============================================================================
/*
return function(value) {
   return out(extractHost(value));
};
*/

🧪 View Test Scenarios (5 tests)

✅ '[example] Extract host with port'
✅ '[example] Extract host without port'
✅ URL with subdomain - should extract full host
✅ URL with query and hash - should extract host only
✅ Invalid URL - should return undefined