The behavior of ASI is fully specified. Semicolons are optional. There is no undefined behavior in the language spec that makes using semicolons somehow safer.
Furthermore, even if you always write semicolons you are still subject to ASI modifying your code by inserting additional semicolons where you don’t want them. So you need to learn the rules of ASI regardless of whether you use semicolons or not. https://feross.org/never-use-semicolons/
No mention of strict mode in the section of ASI. Could have sworn that the ASI issues I’ve ran into in the past was resolved by using strict mode, not sure what I’ve got that from.
Furthermore, even if you always write semicolons you are still subject to ASI modifying your code by inserting additional semicolons where you don’t want them. So you need to learn the rules of ASI regardless of whether you use semicolons or not. https://feross.org/never-use-semicolons/