Find if object is changed in pre-save hook mongoose

Question

I am trying to find if the object is changed in pre-save and do some actions accordingly. Followinfg is my code

var eql = require("deep-eql");

OrderSchema.post( 'init', function() {
    this._original = this.toObject();
});

OrderSchema.pre('save', function(next) {
    var original = this._original;

    delete this._original;
    if(eql(this, original)){
        //do some actions
    }
    next();
});

It returns false even when I don't change anything!

Solution

First of all, you don't need the original object at all. You can access it in the pre hook via this. Secondly post hook executes only after all pre hooks are executed, so your code doesn't make any sense at all (check mongoose docs).

You can do the check by checking isModified in your pre hook and remove the post hook at all.

OrderSchema.pre('save', function(next) {    
    if(!this.isModified()){
        //not modified
    }
    next();
});

Update

In order to check if some property was modified, pass property name as a parameter to isModified function:

if (this.isModified("some-property")) {
  // do something
}

Comments

[andersfylling]

Any idea how to check a object variable? eg. this.something.isModified() gives me an undefined error

[andersfylling]

Have you checked that it works? Cause I get an error and this post says otherwise: stackoverflow.com/questions/31173516/…

[Vsevolod Goloviznin]

@sciencefyll I was looking here: mongoosejs.com/docs/api.html#document_Document-isModified

[andersfylling]

Document and Schema doesnt share the same methods

[Vsevolod Goloviznin]

@sciencefyll what mongoose version are you using? I've just checked this code with v4.2.5 and this.isModified("property") is working fine.

[andersfylling]

4.4.12. I'm going to create a new question addressing this, as I might be doing something horrible wrong without realising it.

[andersfylling]

Let us continue this discussion in chat.

[Suhayb]

this in schema pre refers to model not doc, though isModified() wont work unless you change the hook status to post then this became a doc