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JS 6.9 task1 Spy decorator

<HTML>
  <body>
  </body>
   <script>

function work(a,b){
  alert(a + b);
}

function spy(func){

  function wrapper (...args) {
    //to make parameters to be each array by every call
    wrapper.calls.push(args);
    //this is call forwarding : wrapper passes everything it gets
    //and return back its result
    return func.apply(this, arguments);
    //arguments is reserved word,
    // means all argument the outter object has got
  }//function definition can be anywhere in the block
  wrapper.calls = []; //calls is an array
  return wrapper;
}

work = spy(work);
//now work has the body of wrapper
//which has an array calls, and does push everytime it runs
work(1, 2); // 3
work(4, 5); // 9

for (let args of work.calls) {
  alert( 'call:' + args.join() ); // "call:1,2", "call:4,5"
}
   </script>
</HTML>
<!--
func.call(context, ...args) //spread operater(...) allows
to pass ITERABLE (can iterate but no index) as the likst to call
ITERABLE

func.apply(context, args) // it only accepts arraylike args
ARRAYLIKE

DIFFICULT
-->

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JS 5.5 task6 Create an extendable calculator

<HTML>   <body>   </body>   <script> function Calculator() {   let methods = {     "-" : (a, b) => a - b,     "+" : (a, b) => a + b   };   //methods is an object which keeps key for operators   //and value to return the actual operation values   //each returns the result of operation that key(operator) does   this.calculate = function (str){     //calculate is one element in the function Calculator     //it takes the string and returns the value     //in the function element list is delimeted by , not ;     let split = str.split(" "),     a = +split[0],     op = split[1],     b = split [2]     if(!methods[op] || isNaN(a) || isNaN(b)) {       return NaN; // error handling     }     return methods[op](a,b);   }   this.addMethod = function(name, func){     methods[name] = func;     //this is how to add new key and ele to object   } } let powerCalc = new Calculator; powerCalc.addMethod("*&
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JS 5.7 task5 Store read dates

<HTML>   <body>   </body>    <script>    let messages = [        {text: "Hello", from: "John"},        {text: "How goes?", from: "John"},        {text: "See you soon", from: "Alice"}    ];    let readMap = new WeakMap();    alert(readMap.size);    readMap.set(messages[0], new Date(2019, 3, 5));   </script> </HTML> <!-- task4 needed weakSet to save simply readmessage, this task needs to save THE TIME IT WAS READ along with the message itself the message out of the set or map means it hasn't been read I kinda feel good and bad at the same time to happen to read the solution but I do get to think more about the difference with tasks and be more available to understand the main contents so I think, its good? -->
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How to set base url when deployed in Heroku? : base url and axios

https://stackoverflow.com/questions/47164330/axios-api-calls-in-heroku/47165888 baseUrl = process.env.baseURL || "http://localhost:5000" Even more stable way https://stackoverflow.com/questions/52129849/how-to-get-the-base-url-variable-on-a-deployed-heroku-node-app const production  = 'https://examplePage.com'; const development = 'http://localhost:3000/'; const url = (process.env.NODE_ENV ? production : development); process.env.NODE_ENV will resolve to undefined if you are running on localhost production mode. and return production if you have deployed the app production mode.
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