isBlank

Returns true if this char sequence is empty or consists solely of whitespace characters according to Char.isWhitespace.

fun CharSequence.isBlank(): Boolean(source)

fun main() {
    val strings = listOf("   ", "\t\n", "", "Kotlin", "  Kotlin  ")

    strings.forEach { s ->
        println("\"$s\" is blank: ${s.isBlank()}")
    }
}

Source