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JavaScript

yangchun li
yangchun li
14,456 Points
Posted by yangchun li
yangchun li
14,456 Points

Cannot understand the Parameter in function(next) 

// hash password before saving to database
UserSchema.pre('save', function(next) {
    var user = this;
    bcrypt.hash(user.password, 10, function(err, hash) {
        if (err) {
            return next(err);
        }
        user.password = hash;
        next();
    });
});

Where is the parameter coming from? And where do we use it? Is the 'next' in next() the same 'next' as the parameter? what is the next()?

1 Answer

Steven Parker
Steven Parker
229,644 Points
Steven Parker
Steven Parker
229,644 Points

The parameter "next" is a callback to your callback. As you can see from the code defined here, the parameter will be a function that will be called. But this function is itself a callback being passed to the "pre" method of "UserSchema".

So when the "pre" method invokes this callback, it will supply the other callback as the parameter "next". The code that does that is inside the "pre" method (not shown here).