how to avoid external javascript executing more than once?

Question

I have a external js file called main.js which is added in the index page. In some cases that main.js can be included from the another sub page, so it is leading to the execution of main.js twice. my main.js structure main.js

 (function() {
 console.log("js execution started");
//content goes here
//
//
}());

how can i avoid the execution of the main.js twice?

Jonas Wilms · Accepted Answer · 2017-07-19 08:50:16Z

2

set a global variable, and check if its already set, e.g:

var main;
main=main||(function() {
 console.log("js execution started");
 //content goes here
 return 1;
}());

That also gives you the abillity to make an API available via main.

answered Jul 19, 2017 at 8:50

Jonas Wilms

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euvl · Accepted Answer · 2017-07-19 08:51:35Z

1

Try to add a flag to your window (or your global scope) that shows that main.js is already loaded:

(function() {
  if (window.__MAIN_INSTALLED) {
    return
  }

  window.__MAIN_INSTALLED = true
  console.log("js execution started");
}());

answered Jul 19, 2017 at 8:51

euvl

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