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SAJavaScript Strict Mode (“use strict”) Restrictions
1. No implicit global variables
- Variables must be declared using let, const, or var
2. ‘this’ is undefined in functions
- In normal functions, ‘this’ does not refer to global object
3. No duplicate parameter names
- Function parameters must be unique
4. Cannot delete variables or functions
- delete keyword cannot be used on declared variables
5. Octal literals are not allowed
- Example: 010 is invalid
6. Octal escape sequences are not allowed
- Example: “\012” is invalid
7. ‘with’ statement is not allowed
8. Cannot assign to read-only properties
9. Cannot add properties to non-extensible objects
10. eval() has its own scope
- Variables inside eval do not leak outside
11. arguments object restrictions
- No sync between parameters and arguments
12. Reserved keywords cannot be used as variable names
- Examples: let, private, public, interface, etc.
13. Cannot assign to NaN, Infinity, or undefined
14. arguments.callee is not allowed
15. caller and callee access is restricted
16. Safer and stricter function declarations inside blocks
17. Prevents silent errors by throwing exceptions
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