Issue with accessing observable array value by index in KnockoutJS

Recently, I've been attempting to modify the flag value of an item within a complex object. The structure of the object is as follows:

modelData 
    [0]: 
        Main: xz1
        Sub: a,b,c,d,e
        show: true
    [1]:
        Main: xs1
        Sub: g,h,i,j,k
        show: false

My goal is to access this object and switch the flag value - toggling it from true to false and vice versa.

This is the code I attempted to use:

toggleShow: function (item) {
          var index = modelData.indexOf(item);
          modelData[index].show = item.show ? false : true; // should work but sadly doesn't :(
}

The data within the 'item' during the function is represented as:

item
{...}
    __proto__: {...}
    Main: "AXD"
    Sub: [ fg,jk,ik,ko]
    show: true

It's worth noting that 'modelData' is an observable Array.

modelData
function observable() {
        if (arguments.length > 0) {
            // Write

            // Ignore writes if the value hasn't changed
            if (observable.isDifferent(_latestValue, arguments[0])) {
                observable.valueWillMutat
    [Methods]: {...}
    __proto__: {...}
    _id: 168
    _latestValue: [[object Object]]
    _subscriptions: {...}
    arguments: null
    caller: null
    length: 0
    prototype: {...}

Using '_latestValue', I can retrieve the content of the object.

modelData._latestValue
[[object Object]]
    __proto__: []
    length: 1
    [0]: {...}

Although, I have encountered an issue where I am unable to access the value using the element index. Any insights on where I might be going wrong and why I'm facing difficulties in accessing the value by index would be greatly appreciated.

UPDATE:

I have managed to successfully toggle the flag value. However, after updating the flag value, my list in view fails to reflect the changes. Here's the fiddle with the issue here Output:

+ Main1
    hello
    hi
+ Main2
    one
    two

When clicking the plus symbol, the sublist should hide. Clicking again should reveal the sublist once more.

Any suggestions or recommendations would be highly valuable at this point.

Answer №1

To access the underlying array from your observableArray, you must "unwrap" it by calling modelData as a function without any arguments.

Make sure to include the parenthesis before using the index:

toggleShow: function (item) {
          var index = modelData.indexOf(item);
          modelData()[index].show = item.show ? false : true; 
}

Keep in mind that indexOf() works on observableArrays without needing the parenthesis, but for accessing elements at specific indices, the parenthesis are necessary.

If you want the UI to reflect these changes, consider making the 'show' property a ko.observable and updating it like this:

toggleShow: function (item) {
          var index = modelData.indexOf(item);
          modelData()[index].show(item.show() ? false : true); 
}

For your reference, here is the updated code: https://jsfiddle.net/ujs77n7r/

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