setTimeout - how to avoid using string for callback?
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18-09-2019 - |
Question
When using setTimeout
, you have to put the code you want to execute into a string:
setTimeout('alert("foobar!");', 1000);
However, I want to execute a function to which I have a reference in a variable. I want to be able to do this:
var myGreatFunction = function() { alert("foobar!"); };
// ...
setTimeout('myGreatFunction();', 1000);
(Though in real life, the alert is a lengthier bit of code and myGreatFunction
gets passed around as a parameter to other functions, within which the setTimeout
is called.)
Of course, when the timeout triggers, myGreatFunction
isn't a recognised function so it doesn't execute.
I wish javascript let me do this, but it doesn't:
setTimeout(function() { myGreatFunction(); }, 1000);
Is there a nice way round this?
Solution
If you don't need to call myGreatFunction
with any arguments, you should be able to pass setTimeout
a function reference:
setTimeout(myGreatFunction, 1000);
Also, you should always avoid passing setTimeout
code that it needs to evaluate (which is what happens when you wrap the code in quotes). Instead, wrap the code in an anonymous function:
setTimeout(function() {
// Code here...
}, 1000);
See the setTimeout page at the Mozilla Development Centre for more information.
Steve
OTHER TIPS
Who said that it doesn't let you do it?
It does, the code -
setTimeout(function() { myFunction(); }, 1000);
is perfectly valid.