The following function underbar function was rewritten by peer of mine like so:

    var once = function(func) {
        var alreadyCalled = false;
        var result;

        return function() {
          if (!alreadyCalled) {
            result = func.apply(this, arguments);
            alreadyCalled = true;
          }
        return result
        };
      };

Here's how I interpret it. It's a function that takes another function and returns yet another function. If alreadyCalled is false then set result = func.apply(this,arguments)

Can someone please help me understand in a simple way what func.apply(this,arguments) is doing in the context of this function. I can't seem to figure it out!

The following function underbar function was rewritten by peer of mine like so:

    var once = function(func) {
        var alreadyCalled = false;
        var result;

        return function() {
          if (!alreadyCalled) {
            result = func.apply(this, arguments);
            alreadyCalled = true;
          }
        return result
        };
      };

Here's how I interpret it. It's a function that takes another function and returns yet another function. If alreadyCalled is false then set result = func.apply(this,arguments)

Can someone please help me understand in a simple way what func.apply(this,arguments) is doing in the context of this function. I can't seem to figure it out!

• javascript

• store this in variable previous return function... – Bhojendra Rauniyar Commented Feb 12, 2015 at 4:59
• 2 MDN Apply – epascarello Commented Feb 12, 2015 at 4:59

2 Answers 2

remove async await from

React.useEffect(async () => { await something},[]);

then it works just remove async await

React.useEffect(() => { something},[]);

I know your code is different but i got the same issue i remove async from all of the project which was used within useEffect and i dint saw the error again anymore

There are two implicit parameters on every function: this and arguments.

The apply method on the Function object lets you invoke it with those parameters explicitly set.

So what will happen here is that you a get a function wrapping another, and when you call it it will pass down the arguments to the original. It will also keep track if it was called and its result.