public class JavascriptContext

Executes a javascript string and returns the result of the execution as an appropriate object value depending on the type of value that was returned.

Return value types will depend on the Javascript type returned. The following table shows the mappings:

 Javascript TypeJava Return Type


 Numberjava.lang.Double
 Stringjava.lang.String
 Booleanjava.lang.Boolean
 ObjectJSObject
 FunctionJSObject
 nullnull
 undefinednull

Example java //Get the window object JSObject window = (JSObject)ctx.get("window"); // Create a new empty Javascript Object JSObject newObj = (JSObject)ctx.get("{}"); // Get the current document body contents as a string. String html = (String)ctx.get("document.body.innerHTML"); // Get a numerical result Double result = (Double)ctx.get("1+2"); // Get a Javascript function object JSObject func = (JSObject)ctx.get("function(a,b){ return a+b }"); // Get a boolean result Boolean res = (Boolean)ctx.get("1 < 2");

Sets a Javascript value given a compatible Java object value. This is an abstraction upon javascript to execute key = value.

The key is any Javascript expression whose result can be assigned. The value is a Java object that will be converted into a Javascript object as follows:

Java typeConverted to

DoubleNumber IntegerNumber FloatNumber LongNumber StringString JSObjectObject by ref nullnull

Hence if you want to set a Javascript string value, you can just pass a Java string into this method and it will be converted.

JSObject “By Ref”

You may notice that if you pass a JSObject as the value parameter, the table above indicates that it is passed by reference. A JSObject merely stores a reference to a Javascript object from a lookup table in the Javascript runtime environment. It is this lookup that is ultimately assigned to the “key” when you pass a JSObject as the value. This has the effect of setting the actual Javascript Object to this value, which is effectively a pass-by-reference scenario.

Examples

java // Set the window.location.href to a new URL ctx.set("window.location.href", "http://google.com"); // Create a new JSObject, and set it as a property of another JSObject JSObject camera = (JSObject)ctx.get("{}"); ctx.set("window.camera", camera); // Set the name of the camera via JSObject.set() camera.set("name", "My Camera"); // Get the camera's name via Javascript String cameraName = (String)ctx.get("window.camera.name"); // Should be "My Camera" // Set the camera name via context.set() ctx.set("camera.name", "New name"); String newName = (String)camera.get("name"); // Should be "New name"

Calls a Javascript function (encapsulated in a JSObject) with a specified Javascript Object as the “this” context for the function call. Also passes a set of arguments to the method.

This operates almost exactly like the Javascript Function.apply() method.

Note that JSObject also has a couple of call() methods that may be more convenient to use as they will automatically set the “self” parameter to the JSObject callee. This version of the method is handy in cases where you have been passed a function (perhaps as a callback) and you need to execute that function in a particular context.

Example

java // Get the Array.push method as an object JSObject push = (JSObject)ctx.get("Array.prototype.push"); // Create a new array JSObject colors = (JSObject)ctx.get("['red', 'green', 'blue']"); // "Push" a new color onto the array directly using the JSObject's call() // method colors.call("push", "purple"); // Alternate method using JavascriptContext.call() ctx.call(push, colors, "orange"); // Check size of colors array now Double size = (Double)colors.get("length"); // Should be 5.0 // Get 4th color (should be purple) String purple = (String)colors.get(3); // Get 5th color (should be orange) String orange = (String)colors.get(4);

Calls a Javascript function with the given parameters. This would translate roughly into executing the following javascript:

jsFunc.call(self, param1, param1, ..., paramn)

Calls a Javascript function with the given parameters asynchronously. This would translate roughly into executing the following javascript:

jsFunc.call(self, param1, param1, ..., paramn)

Calls a Javascript function with the given parameters asynchronously. This would translate roughly into executing the following javascript:

jsFunc.call(self, param1, param1, ..., paramn)

Calls a Javascript function with the given parameters, and optionally to make the call asynchronously. This would translate roughly into executing the following javascript:

jsFunc.call(self, param1, param1, ..., paramn)

Calls a Javascript function with the given parameters, and optionally to make the call asynchronously. This would translate roughly into executing the following javascript:

jsFunc.call(self, param1, param1, ..., paramn)