If i donot post any array values when i am creating document collection, it should throw an error. like path to "columns" is required. bUt its not giving any error as such(only happening for array).

event_model.js

const mongoose = require('mongoose');

const EventTypes = ['Raw', 'Enriched', 'Joined']
const EventFormats = ["JSON", "DELIMITED", "FIXEDWIDTH", "REGEX"]
const ColumnDataTypes = ["int", "float", "Double", "string"]
const ColumnTypes = ["Description", "ID", "Time"]

var notEmpty = function(columns){
    if(columns.length === 0){console.log("not empty");return false}
    else {console.log("true not empty");return true};
}

const Columns = mongoose.Schema({
    name: {
        type: String,
        required: true
    },
    type: {
        type: String,
        enum: ColumnTypes,
        required: true
    },
    startIndex: {
        type: Number,
        required: true
    },
    endIndex: {
        type: Number,
        required: false
    },
    dataType: {
        type: String,
        enum: ColumnDataTypes,
        required: true
    },
    oldName: {
        type: String,
        required: false
    },
    timeFormat: {
        type: String,
        required: false
    }
});


const filters = mongoose.Schema({
    columns: {
        user_id: {
            type: String,
            required: true
        },
        product_value: {
            type: String,
            required: true
        }
    },
    expressions: {
        type: String,
        required: true
    }
})




const eventSchema = mongoose.Schema({
    _id: mongoose.Schema.Types.ObjectId,
    projectId: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'Project',
        required: true
    },
    type: {
        type: String,
        enum: EventTypes,
        required: isEnriched
    },
    source: {
        type: mongoose.Schema.Types.String,
        ref: 'DataSource',
        required: isRaw
    },
    parentId: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'Event',
        required: isRaw
    }, 
    columns:  [{
        type: mongoose.Schema.ObjectId,
        ref: Columns,
        required: true, //isEnriched
        validate: [notEmpty, 'Please add at least one feature in the features array']
    }],
    regex: {
        type: String,
        required: true
    },
    filters: {type:[filters], required:isEnriched}   // not working
});
/* eventSchema.path('type').validate(fucntion(columns) {
    if (!columns) {
        return false
    } else if (columns.length === 0) {
        return false
    }else (return true;)
    
}, ' random comment'); */

//Validations 

//Check if event is Raw 
function isRaw() {
    if ((this.type) === 'Raw') {
        console.log("inside raw");
        return true;
    }
    console.log("outside raw");

    return false;
}

//Check if event is Enriched
function isEnriched() {
    if ((this.type) === 'Enriched') {
        console.log("inside Enriched");
        return true;
    }
    console.log("outside enriched")
    return false;
}



module.exports = mongoose.model('Event', eventSchema);