Exceptions example. This example was taken from the book "Javascript: The Good Parts".

exception_sample.js

var add = function(a, b){
    var invalidTypes = (typeof a !== 'number' || typeof b !== 'number');
    
    if(invalidTypes){
        throw {
            name: "TypeError",
            message: "add needs numbers"
        };
    }

  return a + b;
};


var tryIt = function ( ){
  try{
    add("bad input");
  } catch(e){
    console.log(e.name);
    console.log(e.message);
  }
};

tryIt( );