Former Israel National Security Advisor Yaacov Amidror said that if Jordan asks for help against ISIS, Israel should help them, during an interview on Galei Tzahal.
If ISIS overruns Jordan, it would create a serious strategic risk for Israel.
Jordan has deployed a large number of army units along the border with Iraq, including tanks, soldiers, missiles launchers. The Jordanian army is probably better trained and prepared than the the Iraqi army. It is also believed that the Iraqi army had ISIS supporters embedded in it, which helped with their quick defeat.
There are rumors that Jordan bought themselves time by quietly cutting a deal with ISIS, so ISIS won’t attack them.