Array To String
Array → string coercion: an array renders as its elements joined by commas, the same way real JS's Array.prototype.toString does. This works through String(arr), a `${arr}` template interpolation, and .join — including for nested arrays, where each nested element renders as its own comma-joined string (recursively).
const nums = [1, 2, 3]
console.log(String(nums)) // 1,2,3
console.log(`nums = ${nums}`) // nums = 1,2,3
const words = ["red", "green", "blue"]
console.log(words.join(" | ")) // red | green | blue
console.log(`${words}`) // red,green,blue
// Nested arrays: each row is String()-ed first, then joined by the separator.
const matrix = [[1, 2], [3, 4], [5, 6]]
console.log(matrix.join("; ")) // 1,2; 3,4; 5,6
console.log(String(matrix)) // 1,2,3,4,5,6
// Arbitrary nesting depth flattens to a single comma-joined string.
const deep = [[[1, 2], [3]], [[4, 5]]]
console.log(String(deep)) // 1,2,3,4,5
// An empty array is the empty string.
const empty: number[] = []
console.log(`[${empty}]`) // []View source on GitHubexamples/arrays/array_to_string.ts