How to execute code not from string using function?

Question

How would I execute code not from a string? Here is an example:

var ready = false;

executeWhen(ready == true, function() {
  console.log("hello");
});

function executeWhen(statement, code) {
  if (statement) {
    window.setTimeout(executeWhen(statement, code), 100);
  } else {
    /* execute 'code' here */
  }
}

setTimeout(function(){ready = true}, 1000);

Could I use eval();? I don't think so, I think that's only for strings.

Don't think of it as code. It's a function, so you call it with (). — Barmar
– Barmar, Commented Mar 24, 2022 at 20:45
Also, executeWhen(ready == true, ...) should be executeWhen(() => ready, ...) so that you can check it repeatedly, not just at the invocation time. — Amadan
– Amadan, Commented Mar 24, 2022 at 20:47

Barmar · Accepted Answer · 2022-03-24 20:54:00Z

3

You call it with code().

You need to change statement to a function as well, so it will get a different value each time you test it.

And when you call executeWhen() in the setTimeout(), you have to pass a function, not call it immediately, which causes infinite recursion.

var ready = false;

executeWhen(() => ready == true, () =>
  console.log("hello"));

function executeWhen(statement, code) {
  if (!statement()) {
    window.setTimeout(() => executeWhen(statement, code), 100);
  } else {
    code();
  }
}

setTimeout(function() {
  ready = true
}, 1000);

answered Mar 24, 2022 at 20:54

Barmar

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2 Comments

Arcadesmasher Over a year ago

Thanks. I'm not familiar with the => syntax though, but thanks!

Barmar Over a year ago

It's an arrow function: stackoverflow.com/questions/24900875/…

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