Israeli here. I'm from mobile so I won't post links but will emphasize the relevant information for you to look up if you wish for sources. I studied this all in the past and writing on the fly

Israel doesn't have a Constitution, but it instead has "Basic Laws", which are generally seen as having the equivalent status and weight of a Constitution's laws. In practice, these basic laws together de facto have a purpose akin to that of a Constitution.

As for why it has these "basic laws" Instead of a constitution; it was, indeed, supposed to have a Constitution - in the declaration of independence (May 1948) it was outlined that a Constitution should be drafted before October 1948. A comitee was created whose purpose was to create a constitution.

This was delayed by two years, to 1950, because of the politics at the time: for one, the deadline was widely unrealistic due to Israel being preoccupied in it's existential War of Independence against the neighboring Arab countries. Furthermore, the different Israeli political parties had widely different visions of what Israel should and would be like, and couldn't come to an agreement.

There's also the fact that it was heavily debated whether a constitution was even necessary; those opposed to a constitution drew examples from other democratic countries lacking a constitution, e.g Britain, and that The Declaration of Independence already contains the values you'd expect to see in a constitution.

Further opposition to the drafting of a constitution grew, ranging from the legal necessity or right of such a document, to the possible risk of a cultural war between the religious and secular populations.

By the time 1950 came around, a compromise decision was reached, called the Harari Decision: In essence, this decision decreed that rather than creating a constitution, the state would create "chapters" of a constitution, called Basic Laws, which at some unspecified point in the future would form the constitution (no deadline set).

Basic Laws are still being created, modified, or removed to this day (example: the controversial 2018 Nation-State law). Theoretically, they will in the future be unified into a single document referred to as a constitution.