ts-extras/distribution/array-concat.js

Essential utilities for TypeScript projects

/**
A strongly-typed version of `Array#concat()` that properly handles arrays of different types.

TypeScript's built-in `Array#concat()` has issues with type inference when concatenating arrays of different types or empty arrays. This function provides proper type inference for heterogeneous array concatenation.

Note: This function preserves array holes, matching the native `Array#concat()` behavior.

@example
```
import {arrayConcat} from 'ts-extras';

const strings = ['a', 'b'];
const numbers = [1, 2];

// TypeScript's built-in concat would error here
const mixed = arrayConcat(strings, numbers);
//=> ['a', 'b', 1, 2]
//   ^? (string | number)[]

// Works with tuples
const tuple = arrayConcat(['x'] as const, [1] as const);
//=> ['x', 1]
//   ^? (1 | 'x')[]

// Handles empty arrays correctly
const withEmpty = arrayConcat([], ['hello']);
//=> ['hello']
//   ^? string[]
```

@category Improved builtin
*/
export function arrayConcat(array, ...items) {
    // Use native concat to preserve holes (flat() would drop them)
    return Array.prototype.concat.call(array, ...items);
}