Why is JIT not enabled on devices like Espruino WiFi even if they are on the latest firmware?

Thank you very much. After a bit of experimenting, I'm currently trying to find out, why the following function hangs indefinitly. It's a function which scans a portion (from this.idx to this.next) of an array for a given sequence, starting at an offset using a given stepping width.

find(sequence, offset, stepping) {
        "jit";
        if (stepping === undefined) {
            stepping = 1;
        }

        if (offset === undefined) {
            offset = 0;
        }

        for (let i = this.idx + offset; i < this.next - sequence.length; i+=stepping) {
            if (this.buffer[i] !== sequence[0]) {
                continue;
            }
            
            let idx = i;

            for (let j = 1; j < sequence.length; j++) {
                if (this.buffer[i + j] !== sequence[j]) {
                    idx = -1;
                    // JIT lacks break statement
                    j = sequence.length - 1;
                }
            }

            if (idx !== -1) {
                return idx;
            }
        }

        return -1;
    }

When I run it without jit it works as expected. If the function is jitted, the application hangs without any error. Thank you for your reply