Does Mongoose provide access to previous value of property in pre('save')?

Question

I\'d like to compare the new/incoming value of a property with the previous value of that property (what is currently saved in the db) within a pre(\'save\') mi

Answer 1

Honestly, I tried the solutions posted here, but I had to create a function that would store the old values in an array, save the values, and then see the difference.

// Stores all of the old values of the instance into oldValues
const oldValues = {};
for (let key of Object.keys(input)) {
    if (self[key] != undefined) {
        oldValues[key] = self[key].toString();
    }

    // Saves the input values to the instance
    self[key] = input[key];
}

yield self.save();


for (let key of Object.keys(newValues)) {
    if (oldValues[key] != newValues[key]) {
       // Do what you need to do
    }
}