How to make a password cracker

Ive been studying JavaScript lately and i have come up to the point where i can make a simple form validation like a username and password. Ive been thinking of making a simple old fashioned and most common method of creating a password cracker, the one which checks for all possible solutions through trial and error. for e.g if someone enters "abc" in the password field, the program automatically enters all possible values one at time and checks them if they are correct.
Now can this be made with basic programming knowledge of python and JavaScript ? Or what im asking for is pretty advanced stuff ?
It'd be helpful if somebody can give me a sample code or something to help me make one

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