Concept:
For negative numbers:
\[
|x|=-x
\]
Hence the given function becomes:
\[
f(x)=\frac{[x]}{-x}
\]
To determine the range, we analyze the function interval by interval.
Step 1: Take \(x\in[-n,-n+1)\).
For this interval:
\[
[x]=-n
\]
where \(n\in\mathbb{N}\).
Therefore:
\[
f(x)=\frac{-n}{-x}
=\frac{n}{x}
\]
Since \(x<0\), the values remain negative.
Step 2: Determine extreme values.
For \(x\in[-n,-n+1)\),
At \(x=-n\),
\[
f(x)=\frac{-n}{n}=-1
\]
As \(x\to(-n+1)^-\),
\[
f(x)\to \frac{-n}{n-1}
\]
which is less than \(-1\).
Thus values extend continuously below \(-1\).
Step 3: Combine all intervals.
For different values of \(n\), the function covers:
\[
(-\infty,-1]
\]
Thus the complete range is:
\[
\boxed{(-\infty,-1]}
\]