The positions of IIFEs (immediately invoked function expressions) of JS cause an unexpected error

Question

The following code including an IIFE causes an error in Node(node: v8.6.0) environment.

function A(){}
A()
(function(){})()

A(...) is not a function

This error information is confusing for me.

If I change the position of IIFE, the code runs successfully in Node.

(function(){})()
function A(){}
A()

I have searched the answer on google but didn't find why.

score 2 · Accepted Answer · answered Apr 18 '18 at 13:16

2

In this snippet:

function A(){}
A()
(function(){})()

you are starting third line with ( which is interpreted by JS parser as a function invocation. In this case automatic semicolon insertion lets you down.

You could try this instead:

function A(){}
A(); // <-----
(function(){})()

or

function A(){}
A()
;(function(){})()

both will fix the problem.

Avoid staring line with ( or [.

answered Apr 18 '18 at 13:16

dfsq

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Splendid. Your answer solved my problem. – A.Chao Apr 18 '18 at 13:21
assigning the result to a variable also solves the problem. const test = (function(){})() – Md. Abu Taher Apr 18 '18 at 13:22

score 0 · Answer 2 · answered Apr 18 '18 at 13:18

0

If you use a ; you can get around this.

Expressions should end with ; to avoid this problem:

function A(){}
A();
(function(){})()

answered Apr 18 '18 at 13:18

Ovidiu Dolha

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The positions of IIFEs (immediately invoked function expressions) of JS cause an unexpected error

2 Answers2