Mongoose not validating in schema

I'm having trouble getting my schema model to validate. My code seems to simply ignore that there are required and validate type is the mode. I created a custom validator to see if the inserted string is = 'below' . Even if I leave the key blank, it will still post the model into the collection.

//modeljs
    var mongoose = require('mongoose');
    var Schema = mongoose.Schema;

    var directionValidator = [
            function (val) {
                console.log(val); //check 
                return (val.toLowerCase() = 'below')
              },
            'Invalid Direction'
            ];
    var directionSchema = new Schema({

    email: {
    type: String,
    required: true,
    validate: requiredStringValidator
},
module.exports = mongoose.model('direction', directionSchema);




//controllerjs
    var newAlert = require('../models/modeljs');
    var mongoose = require('mongoose');
    mongoose.connect('mongoURL');
    var db = mongoose.connection;

exports.create = function (req, res) {
    var entry = new newAlert({       
        direction: req.body.direction

});

db.collection('direction').insert(entry,function(err){
        if (err) {
            var errMsg = "There was an error saveing" + err;
            res.send(errMsg);
    }
    else{
        console.log('no errors saving');
    }
res.send('All inserted')
};

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