need in JavaScript

Write a function: function solution (A, B) that, given a string A consisting of N characters and a string B consisting of M characters, returns the number of times A must be stated such that B is a substring of the repeated string. If B can never be a substring of the repeated A, then your function should return -1. For example, given: A-" abcd" ? "cdabcdab. your function should return 3, because after stating string A three times we obtain the string 'abcdabcdabcd. String B is a substring of this string. Assume that: . N is an integer within the range [1..1000] . M is an integer within the range [1.1000) Tes