有人能解释一下 javaScript 中的“空”语句和普通分号有什么区别吗

Question

Can anyone explain me what is the difference between a normal semicolon; that comes after every statement and the empty statement; in javaScript

console.log(1);/* semicolon */ console.log(2)

and the empty statement that sometimes comes as the body of if, for, while, do-while statements in javaScript eg:

if (true)
 ; /* empty statement */

is there a difference between both a semicolon; and an empty statement;

Answer 1

Each javascript statement should (although not all must) end with a semicolon, 'empty statement' also. A semicolon in an empty statement is just a semicolon that completes the statement.

For the final explanation: 'empty statement' is an statement without any sign hence its name. It must contain a terminating semicolon or the JS parser would not be able to distinguish it from other whitespace characters. Thus, the semicolon sign; It is not an statement but is a mandatory semicolon ending the empty statement.

Answer 2

In JavaScript semicolons indicates the end of a statement. A semicolon is not necessary after a statement if it is written on its own line, although it is considered good practice to do so. But if more than one statement on a line is desired, then they must be separated by semicolons.

//these are ok
console.log(1)
console.log(2);

//this won't run
console.log(1) console.log(2) console.log(3)

//this will run
console.log(1); console.log(2); console.log(3);

An empty statement is used to provide no statement in circumstances where the JavaScript syntax would expect one. For example in a for loop:

for (let i = 0; i < 10; array[i++] = 0)
; //JavaScript requires a statement here so do nothing

Also some JavaScript statements must be terminated with semicolons and are therefore affected by automatic semicolon insertion (ASI). If you wish to deepen more into this I recommend you check this doc and this on MDN. For a better understanding you may check the ECMAScript standard .