Darts are counted as stubble - The word rendered "darts" (תותח tôthâch) occurs nowhere else in the Scriptures. It is from יתח, obsolete root, "to beat with a club." The word here probably means clubs. Darts and spears are mentioned before, and the object seems to be to enumerate all the usual, instruments of attack. The singular is used here with a plural verb in a collective sense.

Darts are counted as stubble - All these verses state that he cannot be wounded by any kind of weapon, and that he cannot be resisted by any human strength. A young crocodile, seen by M. Maillet, twelve feet long, and which had not eaten a morsel for thirty-five days, its mouth having been tied all that time, was nevertheless so strong, that with a blow of its tail it overturned a bale of coffee, and five or six men, with the utmost imaginable ease! What power then must lodge in one twenty feet long, well fed, and in health!

Darts are counted as stubble,.... Darts being mentioned before, perhaps something else is meant here, and, according to Ben Gersom, the word signifies an engine out of which stones are cast to batter down walls; but these are of no avail against the leviathan;
he laugheth at the shaking of a spear; at him, knowing it cannot hurt him; the crocodile, as Thevenot says (g), is proof against the halberd. The Septuagint version is, "the shaking of the pyrophorus", or torch bearer; one that carried a torch before the army, who, when shook, it was a token to begin the battle; which the leviathan being fearless of laughs at it; See Gill on Obadiah 1:18.
(g) Travels, part 1. b. 2. c. 72. p. 245.

Darts--rather, "clubs"; darts have been already mentioned (Job 41:26).