Making field required dynamically based on condition

record.js

({
/* Making field required dynamically based on condition
* Ajay Kumar
* Path : custom/modules/Opportunities/clients/base/views/record/record.js
*/
    extendsFrom: 'RecordView',
    initialize: function(options) {
        this._super('initialize', [options]);
        this.on('render', this.testFunc, this);
        this.model.on('change:probability', this.testFunc, this);
    },
    testFunc: function() {
        var probabilityValue = this.model.get('probability');
        _.each(this.fields, function(field) {
            if (_.isEqual(field.def.name, 'opportunity_type') && _.isEqual(probabilityValue, 10)) {
                field.def.required = true;
            }
        }, this);
    },
})