Check if functionA of one.js exists from two.js

Question

There is an external js which I call in to the main page. This external file has a function

function fruitLib(){
   //do stuff
}

I have another external js and there is another function.

function price(){
   //do stuff
}

Now how can I check if fruitLib() exists before calling price()? Below is what I tried but doesn't work (maybe because both files are external files).

if (typeof fruitLib== 'function') { 
  price(); 
}

Your check is fine if fruitLib is a global function. Can you provide more information? — T.J. Crowder
– T.J. Crowder, Commented Nov 30, 2015 at 10:53
@T.J.Crowder Thanks for your reply. None of them are global functions. I just have functionA in one.js and I want to call function of two.js only if functionA is available. — Becky
– Becky, Commented Nov 30, 2015 at 10:56
For it to be available, it must either be a global function or a value you receive as the result of a function call (for instance, using some kind of AMD). — T.J. Crowder
– T.J. Crowder, Commented Nov 30, 2015 at 10:57
Thanks. If price() is in the main html file, is it possible to check if fruitLib() is available? — Becky
– Becky, Commented Nov 30, 2015 at 11:00
As I said: The check you have will work. It will work if fruitLib is a global, and it will work if fruitLib is a variable you've received a function reference into. The question makes no sense at present. — T.J. Crowder
– T.J. Crowder, Commented Nov 30, 2015 at 11:09

Community · Accepted Answer · 2017-05-23 11:52:20Z

2

Assuming that fruitLib() is in file foo.js and price() in bar.js, do this in the area that you include your JavaScript files:

<script src="foo.js">
<script src="bar.js">

That way you know that fruitLib() is loaded before price().

A relevant question lies here: Javascript check if function exists.

edited May 23, 2017 at 11:52

CommunityBot

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answered Nov 30, 2015 at 10:51

gsamaras

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2 Comments

Becky Over a year ago

Thanks. Is it possible to check iffruitLib() is available, if price() is in the main html itself?

gsamaras Over a year ago

Becky you are welcome, it's a nice question, that's why I am upvoting! Well doesn't the link helps? I have a class now. If you still have issues let me know.

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