isArrayIndex

Determines whether a string represents a valid array index. Performs character-by-character validation to check if a string consists entirely of numeric digits, making it suitable for use as an array index. Optimized for performance with manual character code checking.

Signature

const isArrayIndex: (value: string) => boolean

Parameters

Name	Type	Description
value	-	String to test for valid array index format

Returns

Boolean indicating whether the string is a valid array index

Examples

Valid array index strings

import { isArrayIndex } from '@winglet/common-utils';

console.log(isArrayIndex('0')); // true
console.log(isArrayIndex('123')); // true
console.log(isArrayIndex('999')); // true
console.log(isArrayIndex('42')); // true

// Invalid array index strings
console.log(isArrayIndex('')); // false (empty string)
console.log(isArrayIndex('01')); // false (leading zero, but still digits)
console.log(isArrayIndex('12.5')); // false (contains decimal point)
console.log(isArrayIndex('abc')); // false (contains letters)
console.log(isArrayIndex('12a')); // false (mixed alphanumeric)
console.log(isArrayIndex('-5')); // false (negative number)
console.log(isArrayIndex(' 123 ')); // false (contains spaces)

Object property validation

function processObjectProperties(obj: Record<string, any>) {
  for (const key in obj) {
    if (isArrayIndex(key)) {
      console.log(`Array-like index: ${key} = ${obj[key]}`);
    } else {
      console.log(`Named property: ${key} = ${obj[key]}`);
    }
  }
}

// Usage
processObjectProperties({
  '0': 'first',
  '1': 'second',
  'name': 'John',
  '12': 'twelve'
});

Dynamic array access validation

function safeArrayAccess(arr: any[], key: string): any {
  if (isArrayIndex(key)) {
    const index = parseInt(key, 10);
    return arr[index];
  }

  console.warn(`Invalid array index: ${key}`);
  return undefined;
}

Form data processing

function parseFormArrayData(formData: Record<string, string>) {
  const arrayItems: string[] = [];
  const namedFields: Record<string, string> = {};

  for (const [key, value] of Object.entries(formData)) {
    if (isArrayIndex(key)) {
      arrayItems[parseInt(key, 10)] = value;
    } else {
      namedFields[key] = value;
    }
  }

  return { arrayItems, namedFields };
}

Playground

import { isArrayIndex } from '@winglet/common-utils';

console.log(isArrayIndex('0')); // true
console.log(isArrayIndex('123')); // true
console.log(isArrayIndex('999')); // true
console.log(isArrayIndex('42')); // true

// Invalid array index strings
console.log(isArrayIndex('')); // false (empty string)
console.log(isArrayIndex('01')); // false (leading zero, but still digits)
console.log(isArrayIndex('12.5')); // false (contains decimal point)
console.log(isArrayIndex('abc')); // false (contains letters)
console.log(isArrayIndex('12a')); // false (mixed alphanumeric)
console.log(isArrayIndex('-5')); // false (negative number)
console.log(isArrayIndex(' 123 ')); // false (contains spaces)

Notes

Validation Rules:

• Must contain only digits (0-9)
• Cannot be empty string
• No leading/trailing whitespace allowed
• No decimal points or negative signs
• Leading zeros are technically valid (returns true)

Performance Optimization:

• Uses character code checking (48-57 for digits 0-9)
• Avoids regex or parsing overhead
• Early termination on first non-digit

Use Cases:

• Object property iteration and classification
• Dynamic array access validation
• Form data processing
• Array-like object detection

Note: This function only validates string format, not actual array bounds. Use additional bounds checking when accessing arrays.