selectFromArray — GTM Variable Template for Array

VARIABLES › ARRAY

selectFromArray CORE Array

Direct (.tpl) Apply (.tpl)

Selects an element from the array based on the provided index. Returns undefined if invalid.

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When to Use This

Array Processing

Iterate, filter, map, and reshape arrays of items for batch data operations.

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Examples

Select by index▶ Try

INPUT

Array To Select From: ['apple', 'banana', 'cherry', 'date']
Index: 2

OUTPUT

cherry

Out of bounds returns undefined▶ Try

INPUT

Array To Select From: [1, 2, 3]
Index: 10

OUTPUT

undefined

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GTM Configuration

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selectFromArray

Read-Only Try Live

Array To Select From

💾 The array from which to select an element.

Supported formats:
  ✓ Array

Index

🎯 The index of the element to select.

Supported formats:
  ✓ Number
  ✓ 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.

Array To Select From array

💡 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]

Index number

🔗 Result Handling — Chain Variables

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

selectFromArray()

+ Chain another variable

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Related Variables

Same category: Array

→ chunk → compact → dropItems → dropItemsRight → every → filterArray → find → findIndexByCallback → findIndexByRegex → flatten → head → includesAll → includesAny → includesNone → indexOf → join → last → lastIndexOf → reduce → reduceRight → reverse → some → sort → tail → takeItems → takeItemsRight → uniq → wrapInArray

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Under the Hood

📜 View Implementation Code

/**
* Selects an element from the array based on the provided index.
* 
* @param {Array} data.src - The array from which to select an element.
* @param {number|string} data.idx - The index of the element to select.
* @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 selection.
* 
* @returns {any} The selected element at the specified index, or undefined if the index is invalid or array is not valid.
*
* @framework ggLowCodeGTMKit
*/
const getType = require("getType");
const makeNumber = require('makeNumber');

const selectFromArray = function(array, index) {
   if (getType(array) === 'array') {
       const idx = makeNumber(index);
       return array[idx]; 
   }
   return undefined;
};
const safeFunction = fn => typeof fn === 'function' ? fn : x => x;
const out = safeFunction(data.out);
// ===============================================================================
// selectFromArray - Direct mode
// ===============================================================================
const applyCast = (castFn, value) => safeFunction(castFn)(value);
const value = applyCast(data.pre, data.src);
return out(selectFromArray(value, data.idx));
// ===============================================================================
// selectFromArray(...) – Apply Mode
// ===============================================================================
/*
return function(value, index) {
   index = data.rp1 ? data.idx : index;
   return out(selectFromArray(value, index));
};
*/

🧪 View Test Scenarios (6 tests)

✅ '[example] Select by index'
✅ String index parameter - converts to number and selects element
✅ Index zero - returns first element
✅ '[example] Out of bounds returns undefined'
✅ Non-array input - returns undefined
✅ Non-integer index - returns undefined