Future JavaScript: what is still missing?(2ality.com)

    const func = (() => {
      let result; // cache
      return () => {
        if (result === undefined) {
          result = someComputation();
        }
        return result;
      }
    })();

    let result;
    const func = () => {
      if (result === undefined) {
        result = someComputation();
      } 
      return result;
    }

    const value = do {
      switch (someString) {
        case 'Monday':
          0;
          break;
        case 'Tuesday':
          1;
          break;
        ...
      }
    }

    const other = do {
      if (isPrime(n)) {
        'prime'
      } else if (isOdd(n)) {
        'odd'
      } else {
        'even'
      }
    }

    function memoize = function (fn) {
        var value
        return function() {
            return value !== undefined ? value : (value = fn())
        }
    }

    var func = memoize(someComputation)

    +value|0

  getFooOfBar(this_bar:hasfoo) => this_bar.foo

  function getFoo() {
    return this.foo;
  }

  if(let [x,y] = thing) ...

    var style = {
      font-size: 10px, 
      border-width: 1em
    }  

   this.timer(200ms, function() {...});
   
   element.style.width = 1em;
    
   var c = rgb(128,128,0);
   assert c.r == 128; 
   var (h,s,v) = c.toHSV();

    1 in [1,2,3] -> true
    
    "foo" in {foo:1,bar:2}  -> true

    namespace Foo 
    {
      function a() { return "a"; }  
      function b() { return a(); } // Foo.a() call
    } 

    namespace Key { // enums
      const ENTER = 13;
      const SPACE = 32;
    } 

    if( evt.keyCode == Key.ENTER ) 
      ...

   [1,2,3] == [1,2,3] -> true in Sciter, false in JS
   [1,2,3] === [1,2,3] -> false in Sciter and in JS

   {a:1} == {a:1} -> true in Sciter, false in JS
   {a:1} === {a:1} -> false in Sciter and in JS

    _.range(5).forEach(i => {/*...*/})

    Array(5).fill().forEach(() => console.log('hello'))

   for (var n in 5) // n is in [0..5)

    [1, 2, 3] + [1] == [1, 2, 3, 1]