activex-helpers

Event handler management, and parameterized property setters, for ActiveX objects

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Also available via npm.
Event handler management
There are a number of mechanisms for handling ActiveX events in Javascript; however, they all require that:
  • the variable must be initialized before the function declaration is evaluated. This is harder than it seems, because of function declaration hoisting; and requires doing one of the following:
* wrap the function declaration within an IIFE (this works because function declarations are only hoisted to the function scope),
* some form of string-to-code evaluation -- `eval`, `setTimeout`, `window.execScript`, `new Function`, or
* wrap the function within a `SCRIPT` block, while the initialization happens before the `SCRIPT` block (either in another `SCRIPT` block, or by setting the `id` of a previous element); this also implies that the `id`/variable must be available to the global scope.
  • the function must have a special name -- depending on the environment and event handling mechanism, either variable.eventName, variable::eventName, or variable_eventName
  • the parameters of the function must exactly match those defined in the ActiveX event
``` var wdApp = new ActiveXObject('Word.Application'); //using eval eval('function wdApp::Quit() {window.alert(\'Application quit\');}'); //using an IIFE (function() { function wdApp::Quit() {
window.alert('Application quit');
} })(); ``` This library enables the following: ``` (function() { var wdApp = new ActiveXObject('Word.Application'); //using a function expression, without a special name ActiveXObject.on(wdApp, 'Quit', function() {
window.alert('Application quit');
//`this` binding
window.alert(this.Version);
}); //when the event is defined as passing parameters, the parameters are wrapped into a single object //the object is passed into the final event handler //AFAIK there is no way to determine the parameters at runtime, so the names must be passed in at registration ActiveXObject.on(wdApp, 'DocumentBeforeSave', 'Doc','SaveAsUI','Cancel', function (params) {
//changes to the `params` object are propagated back to the internal handler
params.SaveAsUI = false;
params.Cancel = !window.confirm("Do you really want to save?");   
}); })(); ```
Property setter
Property getters and setters without parameters are represented as Javascript simple read/write properties. However, while getters with paraneters are represented as methods, setters with parameters are represented as assignment to methods. ``` var dict = new ActiveXObject('Scripting.Dictionary'); //setter with parameters dict.Item('a') = 1; ``` This is non-standard Javascript. The library enables calling setters with parameters in a standard Javascript-compliant fashion: ``` ActiveXObject.set(dict, 'Item', 'a', 1); ```
Usage
This library relies on a number of ES5 array methods. The necessary shims are available in shims.js, in the absence of another shim library.