Help with JavaScript find and replace

I'm trying to use the Browser's Execute JavaScript action to set a text object to a result string from a JavaScript find and replace operation. Here's what I'm putting in the expression:

Browser.ExecJS(TextInput.Text&"replaceAll(""' ', '+')")

When I preview the project, the Text object just says "0". Any help?

I don't understand what you are trying to do.

There is a native Construct expression which you can use, you don't need JS. For example:

TextInput set text to replace(Self.text, "A", "B")