Creating a....

FooTranspiler.js

var BaseListener = require('./FooListener').FooListener;

function FooTranspiler() {
	BaseListener.call(this);
	
	this.output = "";
}

FooTranspiler.prototype.enterAssignStmt = function(ctx) {
	var target = ctx.ID().getText();
	var value = this.resolveExpr(ctx.expr());
	this.output += "var " + target + " = " + value + ";";
};

FooTranspiler.prototype.enterInvocationStmt = function(ctx) {
	var functionName = ctx.name.text;
	this.output += functionName + "(";
	var expressions = ctx.expr();
	
	for (var i = 0; i < expressions.length; i++) {
		if (i > 0) {
			this.output += ", ";
		}
		
		this.output += this.resolveExpr(expressions[i]);
	}
	
	this.output += ");";
};

FooTranspiler.prototype.resolveExpr = function(ctx) {
	if (ctx.INT() != null) {
		return ctx.INT().getText();
	} else if (ctx.ID() != null) {
		return ctx.ID().getText();
	} else if (ctx.STRING() != null) {
		// Replace any occurrence of ${expr}
		// with " + expr + "
		// i.e.
		// "Hello, ${user}!" -> "Hello, " + user + "!"
		return ctx.STRING().getText().replace(/\$\{([^\}]+)\}/g, '" + $1 + "');
	} else return "undefined";
}

module.exports = FooTranspiler;