It is commonly assumed that the story of Jephthah's vow refers to an 'old tradition' that was integrated into the Deuteronomistic History. But such a view is contrary to Dtr ideology which is absolutely hostile to any human sacrifice (2 Kgs 16.3; 17.17, 31; 21.6 etc.). A literary-critical approach to Judges 11 shows that vv. 30-31 [32] and 34-40 may be considered as post-Dtr.
The author of Judg. 11.30-40 seems to know the story of the Aqedah, but he is not willing to make a happy ending. There is a tragic dimension in the story and quite an Hellenistic atmosphere (the best parallels to Judg. 11.30-40 may be fou Hellenistic nd in texts). So this text should be considered an insertion from the end of the Persian or beginning of the Hellenistic periods. The author tends to show that Jewish classics can be as tragic as Greek ones.