I wish JavaScript had built-in immutable data structures. Immutable.js is interesting, but difficult to bring into a project because it's difficult to get buy-in from everyone involved.

I also wish JavaScript were generally better at functional programming - I'd love to see a keyword that ensures that no form of mutation is possible within a given scope.

I resisted immutability until I really understood that many of my bugs were because of mutation - now I'm a big advocate.

I'd REALLY like to be able to query deeply nested object attributes without having to test every single level of the object hierarchy to find if the attribute exists.

Function level scope would be great too - it would be good to conditionally declare and set variables in a function without needing to pre-declare the variable outside the condition test.

Remove the need of parentheses on if else statements

if foo === 'FOO' && bar > 7 {

  console.log(bar)

  return true

}else if typeof foo === 'string'{

  return false

}

return null

I wish javascript could handle operator overload. not only basic operator, also any custom. something like: objectClass.prototype.operator like = function(a,b) {...} objectClass3 = objectClass1 like objectClass2; Object.defineOperator(objectClass.prototype,"like",{ priority: 10, type: "binary", callback : function(a,b) { ... } });

not a change to an existing thing but i have a feature idea: variables that aren't initialized until the first time they're accessed

  textarea.onkeydown = event => {
  
    // doesn't get the properties until they're accessed
    const get {selectionStart, selectionEnd, value} = textarea;
  
    // doesn't actually call .slice yet
    const get selectedText = value.slice(selectionStart, selectionEnd);
  
    // ...
  
    if (event.key === "Enter") {
  
      // initializes selectedText
      console.log("selected text: " + selectedText);
  
      // uses the same value, doesn't reinitialize it
      selectedText;
    }
  };

make the syntax more like swift or java, remove the concept of prototype.