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Madura Harshana
Madura Harshana

Reputation: 1299

what is the equivalent JavaScript function for VBScript CreateObject()

What is the JavaScript equivalent function for CreateObject("Scripting.Dictionary")? I have to convert following two statements from VBScript to JavaScript, anyone can help me to find a solution.

Set oInvoicesToCreate = CreateObject("Scripting.Dictionary")
If Not oInvoicesToCreate.Exists(cInvoiceID) Then
     oInvoicesToCreate(CStr(cInvoiceID)) = ""
End If

Upvotes: 0

Views: 3504

Answers (2)

Zev Spitz
Zev Spitz

Reputation: 15297

As bluetoft says in this answer, in Javascript you can use a plain object instead. However, there are a few differences between them that you should be aware of:

First, a Dictionary's keys can be any type:

var dict = new ActiveXObject('Scripting.Dictionary');
dict(5) = 'Athens';
console.log(dict('5')); //prints undefined

whereas any value used for a Javascript object's key will be converted to a string first:

var obj = {};
obj[5] = 'Athens';
console.log(obj['5']); // prints 'Athens'

From MDN:

Please note that all keys in the square bracket notation are converted to String type, since objects in JavaScript can only have String type as key type. For example, in the above code, when the key obj is added to the myObj, JavaScript will call the obj.toString() method, and use this result string as the new key.

Second, it is possible to set a Dictionary to treat differently cased keys as the same key, using the CompareMode property:

var dict = new ActiveXObject('Scripting.Dictionary');
dict.CompareMode = 1;
dict('a') = 'Athens';
console.log(dict('A')); // prints 'Athens'

Javascript key access via [] doesn't support this, and if you want to treat differently-cased keys as the same, you'll have to convert the potential key to lowercase or uppercase before each read or write.

For your specific scenario, neither of these differences matter, because the keys are numeric strings (1) which have no case (2).

Upvotes: 0

bluetoft
bluetoft

Reputation: 5443

var oInvoicesToCreate = {};
if(oInvoicesToCreate[cInvoiceID] === undefined){
    oInvoicesToCreate[cInvoiceID] = "";
}

You probably don't want to check the hasOwnProperty method because you'll want to check if anything in the prototype chain has that property as well and not overwrite it. checking with the []s will let you know if any property on any prototype items have the property as well.

Upvotes: 3

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