Uniform convergence — where a steepening ramp converges uniformly

For each positive integer $n$, let $f_n:[-1,1]\to\mathbb{R}$ be given by $f_n(x)=-1$ if $-1\le x\le-\frac1n$, $f_n(x)=nx$ if $-\frac1n<x<\frac1n$, and $f_n(x)=1$ if $\frac1n\le x\le1$. On which of the following intervals does the sequence $\{f_n\}_{n\ge1}$ converge uniformly?