Hydrides of alkaline/alkaline earth elements (s-block elements) are almost* always ionic because the cations are very electropositive forming a strong ionic bond. Hence, they are called ionic/salt like hydrides
The hydrides of p-block elements are not very strong and are non-ionic, hence they are considered covalent hydrides.
*The key word almost is because beryllium hydride is the only s-block hydride which is covalent. $\ce{BeH2}$ is also the only known s-block hydride which can't be made by direction reaction of beryllium and hydrogen (unlike other s-block hydrides which are made by direct metal and hydrogen interaction)
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