Question

71

Access JSON or JS property using string

rated 0 times [ 73] [ 2] / answers: 1 / hits: 27388 / 13 Years ago, thu, august 11, 2011, 12:00:00

I have a JSON array like this:

_htaItems = [

    {ID:1,

     parentColumnSortID:0,

     description:Precondition,

     columnSortID:1,

     itemType:0},

    {ID:2,

     parentColumnSortID:0,

     description:Precondition,

     columnSortID:1,

    itemType:0}]

I want to update this by passing the ID, column name and new value to a function:

    function updateJSON(ID, columnName, newValue)

    {

        var i = 0;

        for (i = 0; i < _htaItems.length; i++)

        {

            if (_htaItems[i].ID == ID)

            {

                ?????

            }

        }

    }

My question is, how do I update the value? I know I can do something like the following:

 _htaItems[x].description = 'New Value'

But in my cause, the column name is being passed as a string.

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johannatorim

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3 Years ago

answered 13 Years ago myrap · Accepted Answer

In JavaScript, you can access an object property either with literal notation:

the.answer = 42;

Or with bracketed notation using a string for the property name:

the[answer] = 42;

Those two statements do exactly the same thing, but in the case of the second one, since what goes in the brackets is a string, it can be any expression that resolves to a string (or can be coerced to one). So all of these do the same thing:

x = answer;

the[x] = 42;



x = ans;

y = wer;

the[x + y] = 42;



function foo() {

    return answer;

}

the[foo()] = 42;

...which is to set the answer property of the object the to 42.

So if description in your example can't be a literal because it's being passed to you from somewhere else, you can use bracketed notation:

s = description;

_htaItems[x][s] = 'New Value';