Dynamically Updated Multiple Choice upon Drop Down value

Forms Public Forms
1

I have implemented the code suggested but it's not working for me:
(I don't understand the difference between options and value)

I want to precompile a Multiple Choice upon the values of three Drop Down

function ShowActionTaken2() {
fd.field('MultipleChoice1').options=fd.field('DropDown1').value;
fd.field('MultipleChoice1').options=fd.field('DropDown2').value;
fd.field('MultipleChoice1').options=fd.field('DropDown3').value;
}

fd.field('MultipleChoice1').$on('change', function(value) {
$fd.field(value).$parent.$el).hide();
$(fd.field('HL' + value).$parent.$el).hide();
if(fd.field('MultipleChoice1').value.includes(value)){
$(fd.field(value).$parent.$el).show();
$(fd.field('HL' + value).$parent.$el).show();
}
});

fd.field('DropDown1').$on('change',ShowActionTaken2);
fd.field('DropDown2').$on('change',ShowActionTaken2);
fd.field('DropDown3').$on('change',ShowActionTaken2);

2

Dear @gaigam,
Please, use the following code:

function updateOptions(){
    var options = [];
    options.push(fd.field('DropDown1').value);
    options.push(fd.field('DropDown2').value);
    options.push(fd.field('DropDown3').value);
    fd.field('MultiChoice1').options = options;
}

fd.rendered(function(){
    //update options on load
    updateOptions();
    //update options on change of any of the fields
    fd.field('DropDown1').$on('change', function(){
        updateOptions();
    });
    fd.field('DropDown2').$on('change', function(){
        updateOptions();
    });
    fd.field('DropDown3').$on('change', function(){
        updateOptions();
    });
})

The difference between value and options is simple. Value is what is currently selected, while options is what is available for the selection in MultiChoice field.