Mongoose allows you to configure custom setters in which you do the comparison. pre(‘save’) by itself won’t give you what you need, but together:

schema.path('name').set(function (newVal) {var originalVal = this.name;if (someThing) {this._customState = true;}
});
schema.pre('save', function (next) {if (this._customState) {...}next();
})

或者

var Person = new mongoose.Schema({name: {type: String,set: function(name) {this._previousName = this.name;return name;}
});Person.pre('save', function (next) {var previousName = this._previousName;if(someCondition) {...}next();
});