Semicolon before (()=>true)()

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It works fine:

const foo = 1; // any number, string, bolean or object
(() => console.log('stuff'))()

But it doesn't work without semicolon:

const foo = 1 // TypeError: 1 is not a function
(() => console.log('stuff'))()

Hm... Should not the call of an anonymous function be treated as a separate instruction in the case when the first bracket can not be interpreted as a correct continuation of the previous instruction?

Yes, but it's only about syntactically correct continuations.

1(() => console.log('stuff'))()

is a syntactically correct expression and parses as "call 1 with an argument of () => console.log('stuff'), then call the result of that without arguments". This throws an exception at runtime (1 is not function, so it can't be called), but it's still a valid expression.

Semicolons: A Quick Guide How to Use a Semicolon, You can use a semicolon to join two closely related independent clauses. Let's put that another way. The group of words that comes before the semicolon should​  You should use a semicolon before a conjunctive adverb, not after. Final Thoughts: How and When to Use a Semicolon. A semicolon is a unique type of punctuation mark used to join independent clauses or divide items in a list. In many instances semicolons can be used interchangeably with periods; however, they have their own rules that govern

You should alway use semicolons. If you do not add them, Javascript will guess where to insert them and will lead to errors.

In your case, it is interpreting that you are calling a function.

A good article on the topic on how semicolons are automatically inserted:

The norm: The parser treats every new token as part of the current statement, unless there is a semicolon that terminates it. The following examples show code where you might think a semicolon should be inserted, but isn’t. This illustrates the risks of omitting semicolons.


a = b + c
(d + e).print()

This does not trigger ASI, because the opening parenthesis could follow c in a function call. The above is thus interpreted as:

a = b + c(d + e).print();

Using semicolons before conjunctions (and, or, but, etc.), When a sentence made up of two independent clauses contains commas, it is possible to use a semicolon before a conjunction which joins the two independent  A semicolon isn’t the only thing that can link two independent clauses. Conjunctions (that’s your ands, buts, and ors) can do that too. But you shouldn’t use a semicolon and a conjunction. That means when you use a semicolon, you use it instead of the ands, buts, and ors; you don’t need both.

…when the first bracket can not be interpreted as a correct continuation of the previous instruction?

But it can - as you can see, the code parses just fine, and executes. That it will throw a runtime exception when no semicolon isn't inserted doesn't matter to the ASI, it cannot know while parsing.

'However' (Period (Full Stop), Comma, or Semicolon Before?), Do not use a comma before 'however' (or any other conjunctive adverb) when it serves as a bridge between two sentences (or independent clauses). You can  Semicolons and commas are used to link two sentences or independent clauses. An independent clause must contain a subject and a verb. You have the choice of leaving one independent clause alone and ending it with a period, or you may link two independent clauses together with either a comma or semicolon.

in javascript, it doesn't matter how many spaces you have, it will just be treated as one space only.

in your second code snippet, it just actually equals:

const foo = 1 (() => console.log('stuff'))()

which means you invoke a function called '1' and pass '()=>console.log('stuff')' as an argument. but apparently 1 is not a function, so it throw an error, hope make sense to you

Use a semicolon before introductory words or connectors, THE SEMICOLON. Use a semicolon to join/separate closely related, complete sentences. The semicolon is stronger than a comma, but weaker than a period  Use a Period (Full Stop) or a Semicolon before "However" A transitional phrase like "however" will usually start a new sentence, but if you would like a smoother transition than that afforded by a period, you can use a semicolon before it to merge the new sentence with the previous one. Here are some examples (transitional phrases shaded):

A Different Meaning for the Period or Semicolon Before "Is That , Deciding to use a period versus a semicolon before “Is that correct?” and expecting your reader to distinguish that they mean something  A semicolon is also often used before introductory expressions such as for example, that is, and namely, in place of a colon, comma, dash, or parenthesis: On one important point Harry and Mabel agreed; that is, it would be better for all if Harry found somewhere else to be while Mabel finished cooking.

The Semicolon, Generally, you should not place a semicolon before a coordinating conjunction that links two independent clauses. The only exception to this guideline is if the  2.) Before a conjunction. When a sentence contains multiple commas in the first clause, it is appropriate to use a semicolon before a conjunction to join two clauses. When too many commas are used in one sentence, the sentence becomes confusing. A semicolon helps to break up the clauses and avoid confusion for the reader. Examples:

Semicolons, colons, and dashes – The Writing Center, Semicolons. The semicolon looks like a comma with a period above it, and this can be a good way to remember what it does. A semicolon creates  The Uses of the Semicolon. The semicolon (;) is a punctuation mark in English separating elements but used much less than the comma. It is more often used in more advanced extended sentences and adds a formal tone. Its name implies that it indicates a separation that is neither full (as indicated by the period), nor minute (as indicated by a comma).