1. Given that the intercepts of line $l$ on the two coordinate axes are opposite numbers, and the distance from point $M(1,-1)$ to $l$ is $\sqrt{2}$. Then the number of lines $l$ that meet the conditions is $\qquad$ lines.
-1.2 .
If the intercepts of line $l$ on both coordinate axes are 0, let the equation of line $l$ be $y=k x$. It is easy to know that $k=1$. Therefore, there is 1 line $l$ that meets the conditions.

If the intercepts of line $l$ on both coordinate axes are $a$ and $-a (a \neq 0)$, then set
$$
l: \frac{x}{a}+\frac{y}{-a}=1 \Rightarrow x-y-a=0 .
$$

By the problem, we have
$$
\frac{|1-(-1)-a|}{\sqrt{1^{2}+(-1)^{2}}}=\sqrt{2} \Rightarrow a=4 \text {. }
$$

Therefore, there is 1 line $l$ that meets the conditions.
In summary, there are 2 lines $l$ that meet the conditions.