add nodejs examples

Author: sebnozzi

examples/nodejs/01-simpleEvaluation.mjs

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+import { Interpreter } from "../../dist/miniscript-ts.mjs"
+
+const interp = new Interpreter();
+let code = `print "Hello " * 3
+            for i in range(1,10); print i; end for`;
+interp.runSrcCode(code);

examples/nodejs/02-contextPersistence.mjs

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+import { Interpreter } from "../../dist/miniscript-ts.mjs"
+
+const interp = new Interpreter();
+let code = `print "Defining function ..."
+sumTwo = function(a,b)
+  return a + b
+end function`;
+interp.runSrcCode(code);
+// Now let's _use_ the function
+code = `print sumTwo(3,2)`;
+// Run new code, but in the same context
+interp.runSrcCode(code);

examples/nodejs/03-accessGlobals.mjs

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+import { Interpreter } from "../../dist/miniscript-ts.mjs"
+
+const interp = new Interpreter();
+let code = `s = "Hello " * 3`;
+interp.runSrcCode(code);
+// Access the globalContext property
+const context = interp.globalContext;
+// Ask for a value by key. Result might be _undefined_.
+const value = context.getOpt("s");
+if (value !== undefined) {
+  console.log("We got from the global context that 's' is:", value);
+}

examples/nodejs/04-addIntrinsic.mjs

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+import { Interpreter } from "../../dist/miniscript-ts.mjs"
+
+const interp = new Interpreter();
+// Use a MiniScript function signature. Default values are supported.
+// Then provide a JavaScript anonymous function. 
+interp.addIntrinsic("mySum(a=0,b=0)", (a, b) => {
+  return a + b;
+});
+// Let's call the intrinsic
+let code = `
+  print mySum(8,4)
+  print mySum(2)`;
+interp.runSrcCode(code);

examples/nodejs/05-addMapIntrinsic.mjs

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+import { Interpreter, newMap } from "../../dist/miniscript-ts.mjs"
+
+const interp = new Interpreter();
+// A typical pattern is to have a map which represents either a "super-type"
+// or a singleton object. In order for this to be accessible one needs to
+// define in turn an intrinsic function that returns such value.
+
+// First we need the map / object.
+// The module exposes a `newMap` function for that!
+const myType = newMap();
+
+// Then we create the intrinsic function to get ahold of it.
+interp.addIntrinsic("MyType", () => {
+  return myType;
+});
+
+// At this point you can do `new MyType` on MiniScript.
+
+// Now let's augment the type with an intrinsic map-function.
+interp.addMapIntrinsic(myType, "someMethod", () => {
+  console.log("Method called!");
+});
+
+// Let's use what we have
+let code = `
+  m = new MyType
+  m.someMethod`;
+interp.runSrcCode(code);

examples/nodejs/README.md

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+
+# Examples for Node.js
+
+At the time of this writing MiniScript.TS is not yet published as an npm package. 
+
+In order to be able to load the examples:
+
+* Build the project using node.js locally
+* Execute the example from the command line (e.g. `nodejs myExample.mjs`, replace with `node` if it applies to you).