Set up constructor for JavaScript object module pattern

Question

Below is my first implementation of a JavaScript object using the Module Pattern. I need to add a constructor to the object, however, and for whatever reason every attempt I make hasn't worked, so I assume I'm setting the object up incorrectly and/or missing some syntax somewhere.

How would I add just a simple, parameter-less constructor to the object below?

var DisplaySettings = {
    //Default display settings for each producer type
    HandleAssignedView: function () {
        var producerType = $('#drpProducerType :selected').text();
        switch (producerType) {
            case "Agency":
                this.AgencyView();
                this.AgencyOptions();
                break;
            case "Sole Proprietor":
                this.NonProducerView();
                this.NonAgencyOptions();
                break;
            default:
                this.ProducerView();
                break;
        }
    },

    //Preserves database values on Edit page load
    LoadAssignedView: function () {
        var producerType = $('#drpProducerType :selected').text();
        switch (producerType) {
            case "Agency":
                this.AgencyView();
                break;
            case "Sole Proprietor":
                this.NonProducerView();
                break;
            default:
                this.ProducerView();
                break;
        }
    },

    AgencyView: function() {
        this.DisplayAgencyFields();
        this.AgencyLabels();
    },

    ProducerView: function () {
        this.DisplayProducerFields();
        this.NonAgencyLabels();
    },

    NonProducerView: function() {
        this.DisplayNonProducerFields();
        this.NonAgencyLabels();
    },

    DisplayAgencyFields: function() {
        $('.AgencyFields').show();
        $('.NonProducerFields').show();
        $('.NonAgencyFields').hide();
        $('.ProducerFields').hide();
    },

    DisplayProducerFields: function () {
        $('.AgencyFields').hide();
        $('.NonProducerFields').hide();
        $('.NonAgencyFields').hide();
        $('.ProducerFields').show();
    },

    DisplayNonProducerFields: function() {
        $('.AgencyFields').hide();
        $('.NonProducerFields').show();
        $('.NonAgencyFields').show();
        $('.ProducerFields').show();
    },

    NonAgencyLabels: function() {
        //Change DRM labels
        $('label[for=DRMCompanyName]').text('DRM Company Name');
        $('label[for=DRMCompanyId]').text('DRM Company Id');

        //Replace header text
        var newval = $('#HeaderText').text().replace("Agency", "Agent");
        $('#HeaderText').text(newval);

        //Adjust fieldset legend text
        $('#AgentTypeFields').children('legend:first').text('Producer Info');
    },

    AgencyLabels: function() {
        //Change DRM labels
        $('label[for=DRMCompanyName]').text('DRM Parent Name');
        $('label[for=DRMCompanyId]').text('DRM Parent Id');

        //Change h2 text to 'Agency' from 'Agent'
        var newval = $('#HeaderText').text().replace("Agent", "Agency");
        $('#HeaderText').text(newval);

        //Adjust fieldset legend text
        $('#AgentTypeFields').children('legend:first').text('Agency Info');
    },

    AgencyOptions: function() {
        $('#JIT').attr('checked', false);
    },

    NonAgencyOptions: function() {
        $('#WelcomeLetter').attr('checked', false);
    }
};

jfriend00 · Accepted Answer · 2014-11-19 20:12:31Z

1

You can do it like this by moving all your methods to the prototype of the constructor:

function DisplaySettings() {
    // constructor initialization code here
}

DisplaySetttings.prototype = {
    //Default display settings for each producer type
    HandleAssignedView: function () {
        var producerType = $('#drpProducerType :selected').text();
        switch (producerType) {
            case "Agency":
                this.AgencyView();
                this.AgencyOptions();
                break;
            case "Sole Proprietor":
                this.NonProducerView();
                this.NonAgencyOptions();
                break;
            default:
                this.ProducerView();
                break;
        }
    },

    //Preserves database values on Edit page load
    LoadAssignedView: function () {
        var producerType = $('#drpProducerType :selected').text();
        switch (producerType) {
            case "Agency":
                this.AgencyView();
                break;
            case "Sole Proprietor":
                this.NonProducerView();
                break;
            default:
                this.ProducerView();
                break;
        }
    },

    AgencyView: function() {
        this.DisplayAgencyFields();
        this.AgencyLabels();
    },

    ProducerView: function () {
        this.DisplayProducerFields();
        this.NonAgencyLabels();
    },

    NonProducerView: function() {
        this.DisplayNonProducerFields();
        this.NonAgencyLabels();
    },

    DisplayAgencyFields: function() {
        $('.AgencyFields').show();
        $('.NonProducerFields').show();
        $('.NonAgencyFields').hide();
        $('.ProducerFields').hide();
    },

    DisplayProducerFields: function () {
        $('.AgencyFields').hide();
        $('.NonProducerFields').hide();
        $('.NonAgencyFields').hide();
        $('.ProducerFields').show();
    },

    DisplayNonProducerFields: function() {
        $('.AgencyFields').hide();
        $('.NonProducerFields').show();
        $('.NonAgencyFields').show();
        $('.ProducerFields').show();
    },

    NonAgencyLabels: function() {
        //Change DRM labels
        $('label[for=DRMCompanyName]').text('DRM Company Name');
        $('label[for=DRMCompanyId]').text('DRM Company Id');

        //Replace header text
        var newval = $('#HeaderText').text().replace("Agency", "Agent");
        $('#HeaderText').text(newval);

        //Adjust fieldset legend text
        $('#AgentTypeFields').children('legend:first').text('Producer Info');
    },

    AgencyLabels: function() {
        //Change DRM labels
        $('label[for=DRMCompanyName]').text('DRM Parent Name');
        $('label[for=DRMCompanyId]').text('DRM Parent Id');

        //Change h2 text to 'Agency' from 'Agent'
        var newval = $('#HeaderText').text().replace("Agent", "Agency");
        $('#HeaderText').text(newval);

        //Adjust fieldset legend text
        $('#AgentTypeFields').children('legend:first').text('Agency Info');
    },

    AgencyOptions: function() {
        $('#JIT').attr('checked', false);
    },

    NonAgencyOptions: function() {
        $('#WelcomeLetter').attr('checked', false);
    }
};

You would then create an object like this:

var settings = new DisplaySettings();

And call methods like this:

settings.LoadAssignedView();

FYI, the usual convention in Javascript is that constructors have initial caps like DisplaySettings, but methods do not have initial caps.

answered Nov 19, 2014 at 20:12

jfriend00

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4 Comments

NealR Over a year ago

Thanks. One more question/things i think I'm missing. I need to attach the HandleAssignedView method to an event handler on a drop down. It can't seem to call any of the methods so long as I place the () syntax after the method name. Is this because those methods are out of scope when calling this as an event (i.e. I'm only attaching the HandloeAssignedView method, none of the ancillary methods), and if so is there a way around this that doesn't break best practices?

jfriend00 Over a year ago

@NealR - To pass a function reference, you would use ONLY settings.HandleAssignedView without any parens after it. Including the parens like settings.HandleAssignedView() calls it now. Without the parens is a reference to the function so it can be called later. Keep in mind that this inside an event handler will be what the event handler sets this to, not your object.

NealR Over a year ago

Ah, that's probably what it is. I'm calling this in the handleAssignedView to call the object methods. What would be the syntax for calling those methods in that context (event handling)? Simply replace this.agencyView() with agencyView()?

jfriend00 Over a year ago

@NealR - It depends upon whether you need the this from the event handler. If you just want to replace this with your object, you can use .bind() when passing the event handler. Instead of passing settings.handleAssignedView, you would pass settings.handleAssignedView.bind(settings). Internally, this creates a stub function that will set up this for you before calling handleAssignedView and the stub function is the actual event handler. You can read about .bind() here.

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