backbone-model-with-readonly-attrs.js

export const Model = BackboneModel.extend({
    /* list of read-only attributes */
    readOnly: [],

    toJSON: function (options) {
        /* convert attributes to JSON but omit the ones from "readOnly" */
        return _.clone(
            return _.omit(BackboneModel.prototype.toJSON.apply(this), this.readOnly)
        )
    }
})

Might want to return _.omit(BackboneModel.prototype.toJSON.apply(this), this.read_only). _.clone is not needed because _.omit already creates a new object.