Do you recommend using semicolons after every statement in JavaScript

Question

In many situations  JavaScript parsers will insert semicolons for you if you leave them out  My question is  do you leave them out   If you re unfamiliar with the rules  there s a description of semicolon insertion on the Mozilla site  Here s the key point      If the first through the nth tokens of a JavaScript program form are grammatically valid but the first through the n 1st tokens are not and there is a line break between the nth tokens and the n 1st tokens  then the parser tries to parse the program again after inserting a virtual semicolon token between the nth and the n 1st tokens    That description may be incomplete  because it doesn t explain  Dreas s example  Anybody have a link to the complete rules  or see why the example gets a semicolon   I tried it in JScript NET    This stackoverflow question is related  but only talks about a specific scenario

User · Accepted Answer

Yes  you should use semicolons after every statement in JavaScript

User · Answer

An ambiguous case that breaks in the absence of a semicolon      define a function var fn   function                     semicolon missing at this line     then execute some code inside a closure  function                        This will be interpreted as   var fn   function                  function                        We end up passing the second function as an argument to the first function and then trying to call the result of the first function call as a function  The second function will fail with a      is not a function  error at runtime

User · Answer

JavaScript automatically inserts semicolons whilst interpreting your code  so if you put the value of the return statement below the line  it won t be returned   Your Code   return 5   JavaScript Interpretation   return  5    Thus  nothing is returned  because of JavaScript s auto semicolon insertion

User · Answer

No  only use semicolons when they re required

User · Answer

The article Semicolons in JavaScript are optional makes some really good points about not using semi colons in Javascript  It deals with all the points have been brought up by the answers to this question

User · Answer

I think this is similar to what the last podcast discussed  The  Be liberal in what you accept  means that extra work had to be put into the Javascript parser to fix cases where semicolons were left out   Now we have a boatload of pages out there floating around with bad syntax  that might break one day in the future when some browser decides to be a little more stringent on what it accepts  This type of rule should also apply to HTML and CSS   You can write broken HTML and CSS  but don t be surprise when you get weird and hard to debug behaviors when some browser doesn t properly interpret your incorrect code

User · Answer

Yes  you should always use semicolons  Why  Because if you end up using a JavaScript compressor  all your code will be on one line  which will break your code   Try http   www jslint com   it will hurt your feelings  but show you many ways to write better JavaScript  and one of the ways is to always use semicolons

User · Answer

What everyone seems to miss is that the semi-colons in JavaScript are not statement terminators but statement separators  It s a subtle difference  but it is important to the way the parser is programmed  Treat them like what they are and you will find leaving them out will feel much more natural   I ve programmed in other languages where the semi-colon is a statement separator and also optional as the parser does  semi-colon insertion  on newlines where it does not break the grammar  So I was not unfamiliar with it when I found it in JavaScript   I don t like noise in a language  which is one reason I m bad at Perl  and semi-colons are noise in JavaScript  So I omit them

User · Answer

What everyone seems to miss is that the semi-colons in JavaScript are not statement terminators but statement separators  It s a subtle difference  but it is important to the way the parser is programmed  Treat them like what they are and you will find leaving them out will feel much more natural   I ve programmed in other languages where the semi-colon is a statement separator and also optional as the parser does  semi-colon insertion  on newlines where it does not break the grammar  So I was not unfamiliar with it when I found it in JavaScript   I don t like noise in a language  which is one reason I m bad at Perl  and semi-colons are noise in JavaScript  So I omit them

User · Answer

The article Semicolons in JavaScript are optional makes some really good points about not using semi colons in Javascript  It deals with all the points have been brought up by the answers to this question

User · Answer

JavaScript automatically inserts semicolons whilst interpreting your code  so if you put the value of the return statement below the line  it won t be returned   Your Code   return 5   JavaScript Interpretation   return  5    Thus  nothing is returned  because of JavaScript s auto semicolon insertion

User · Answer

Yes  you should always use semicolons  Why  Because if you end up using a JavaScript compressor  all your code will be on one line  which will break your code   Try http   www jslint com   it will hurt your feelings  but show you many ways to write better JavaScript  and one of the ways is to always use semicolons

User · Answer

I use semicolon  since it is my habit   Now I understand why I can t have string split into two lines    it puts semicolon at the end of each line

User · Answer

I d say consistency is more important than saving a few bytes  I always include semicolons   On the other hand  I d like to point out there are many places where the semicolon is not syntactically required  even if a compressor is nuking all available whitespace  e g  at then end of a block    if  a    b

User · Answer

I use semicolon  since it is my habit   Now I understand why I can t have string split into two lines    it puts semicolon at the end of each line

User · Answer

No  only use semicolons when they re required

User · Answer

JavaScript automatically inserts semicolons whilst interpreting your code  so if you put the value of the return statement below the line  it won t be returned   Your Code   return 5   JavaScript Interpretation   return  5    Thus  nothing is returned  because of JavaScript s auto semicolon insertion

User · Answer

I d say consistency is more important than saving a few bytes  I always include semicolons   On the other hand  I d like to point out there are many places where the semicolon is not syntactically required  even if a compressor is nuking all available whitespace  e g  at then end of a block    if  a    b

User · Answer

This is the very best explanation of automatic semicolon insertion that I ve found anywhere  It will clear away all your uncertainty and doubt

User · Answer

I think this is similar to what the last podcast discussed  The  Be liberal in what you accept  means that extra work had to be put into the Javascript parser to fix cases where semicolons were left out   Now we have a boatload of pages out there floating around with bad syntax  that might break one day in the future when some browser decides to be a little more stringent on what it accepts  This type of rule should also apply to HTML and CSS   You can write broken HTML and CSS  but don t be surprise when you get weird and hard to debug behaviors when some browser doesn t properly interpret your incorrect code

User · Answer

I use semicolon  since it is my habit   Now I understand why I can t have string split into two lines    it puts semicolon at the end of each line

User · Answer

I think this is similar to what the last podcast discussed  The  Be liberal in what you accept  means that extra work had to be put into the Javascript parser to fix cases where semicolons were left out   Now we have a boatload of pages out there floating around with bad syntax  that might break one day in the future when some browser decides to be a little more stringent on what it accepts  This type of rule should also apply to HTML and CSS   You can write broken HTML and CSS  but don t be surprise when you get weird and hard to debug behaviors when some browser doesn t properly interpret your incorrect code

User · Answer

Yes  you should always use semicolons  Why  Because if you end up using a JavaScript compressor  all your code will be on one line  which will break your code   Try http   www jslint com   it will hurt your feelings  but show you many ways to write better JavaScript  and one of the ways is to always use semicolons

User · Answer

I d say consistency is more important than saving a few bytes  I always include semicolons   On the other hand  I d like to point out there are many places where the semicolon is not syntactically required  even if a compressor is nuking all available whitespace  e g  at then end of a block    if  a    b

User · Answer

I use semicolon  since it is my habit   Now I understand why I can t have string split into two lines    it puts semicolon at the end of each line

User · Answer

Yes  you should always use semicolons  Why  Because if you end up using a JavaScript compressor  all your code will be on one line  which will break your code   Try http   www jslint com   it will hurt your feelings  but show you many ways to write better JavaScript  and one of the ways is to always use semicolons

User · Answer

No  only use semicolons when they re required

User · Answer

I d say consistency is more important than saving a few bytes  I always include semicolons   On the other hand  I d like to point out there are many places where the semicolon is not syntactically required  even if a compressor is nuking all available whitespace  e g  at then end of a block    if  a    b

User · Answer

An ambiguous case that breaks in the absence of a semicolon      define a function var fn   function                     semicolon missing at this line     then execute some code inside a closure  function                        This will be interpreted as   var fn   function                  function                        We end up passing the second function as an argument to the first function and then trying to call the result of the first function call as a function  The second function will fail with a      is not a function  error at runtime

User · Answer

No  only use semicolons when they re required

User · Answer

This is the very best explanation of automatic semicolon insertion that I ve found anywhere  It will clear away all your uncertainty and doubt

User · Answer

I think this is similar to what the last podcast discussed  The  Be liberal in what you accept  means that extra work had to be put into the Javascript parser to fix cases where semicolons were left out   Now we have a boatload of pages out there floating around with bad syntax  that might break one day in the future when some browser decides to be a little more stringent on what it accepts  This type of rule should also apply to HTML and CSS   You can write broken HTML and CSS  but don t be surprise when you get weird and hard to debug behaviors when some browser doesn t properly interpret your incorrect code

User · Answer

JavaScript automatically inserts semicolons whilst interpreting your code  so if you put the value of the return statement below the line  it won t be returned   Your Code   return 5   JavaScript Interpretation   return  5    Thus  nothing is returned  because of JavaScript s auto semicolon insertion

[javascript] Do you recommend using semicolons after every statement in JavaScript?

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