JavaScript is ...

JS is Dynamic

//Compilation and execution happen together.
var propMap = {
 val: "value", html: "innerHTML"
};
for(var fnName in propMap){
	
 $.prototype[fnName] = (function(prop){
 	return function(){
 	 return this[prop];
 	}
 })(propMap[fnName]);
}

JS is Weakly Typed

//Type associated with value, not variable.
var a = 1;
a = "one";
a = [1];
a = {one: 1};

JS has 1st Class Functions

//Treat like any object
var square = function(x){ return x*x }, //create
 	 mult = function(f1, f2){ // Return
 		return function(n){
 		return f1(n)*f2(n);
 		}
 	 },
 	 bigF = mult(square, square), // ARG
value = bigF(2); // 16

JS is Prototype Based