JavaScript free variables

JavaScript free variables

In JavaScript, you can use "delete" To manually delete variables, so that GC (garbage collection) to reclaim memory, but not all variables in JS can be deleted.
1, the global variable "a" of the Var declaration is still "1" after using "delete a".
2. The global variable "B", which was not declared with Var, became the property of "window", and the output error "B is not defined" after using "Delete B".
3, the variable in the object or constructor, the output "undefined" after using "delete".

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