The "unexpected ++" error in jslint
JavascriptJslintJavascript Problem Overview
What is the best practice for that then?
Jslint explains that it "adds confusion". I don't see it really...
EDIT: The code, as requested:
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Javascript Solutions
Solution 1 - Javascript
The longstanding best practice:
Use i += 1
instead, following jslint's advice.
As for why it is a better practice than ++
, according to Crockford:
The increment ++
and decrement --
operators make it possible to write in an extremely terse style. In languages such as C, they made it possible to write one-liners that: for (p = src, q = dest; !*p; p++, q++) *q = *p;
Most of the buffer overrun bugs that created terrible security vulnerabilities were due to code like this. In my own practice, I observed that when I used ++
and --
, my code tended to be too tight, too tricky, too cryptic. So, as a matter of discipline, I don’t use them any more.
Edit: Included comment from Nope as this answer continues to get views. Please continue to upvote his comment as well :)
Solution 2 - Javascript
Just add /*jslint plusplus: true */
in front of your javascript file.
Solution 3 - Javascript
To avoid confusion, and possible problems when using minifiers, always wrap parens around the operator and its operand when used together with the same (+ or -).
var i = 0, j = 0;
alert(i++ +j);
This adds i and j (and increments i as a side effect) resulting in 0 being alerted.
But what is someone comes along and moves the space?
var i = 0, j = 0;
alert(i+ ++j);
Now this first increments j, and then adds i to the new value of j, resulting in 1 being alerted.
This could easily be solved by doing
var i = 0, j = 0;
alert((i++) +j);
Now this cannot be mistaken.
Solution 4 - Javascript
Personally, I prefer to put statements such as i++
on a line by themselves. Including them as part of a larger statement can cause confusion for those who aren't sure what the line's supposed to be doing.
For example, instead of:
value = func(i++ * 3);
I would do this:
value = func(i * 3);
i++;
It also means people don't have to remember how i++
and ++i
work, and removes the need to apply quite so many preference rules.
Solution 5 - Javascript
The real problem of the ++
operator is that it is an operator with side effects and thus it is totally opposed to the principle of functional programming.
The "functional" way to implement i++
would be i = i + 1
where you explicitly reassign the variable with no side effects and then use it.
The possibility of confusion is that ++
does two things by adding a value AND reassigning it to the variable.
Solution 6 - Javascript
JSLint friendly loop
for (i = 0; i < 10; i += 1) {
//Do somthing
}
Solution 7 - Javascript
Please note that the ++ operator depends on position with respect to the prior/next variable and the newline / semicolon to determine order of operations.
var a = 1;
var b = a++;
console.log(b); // b = 1
console.log(a); // a = 2
var a = 1;
var b = ++a;
console.log(b); // b = 2
console.log(a); // a = 2
Solution 8 - Javascript
There is something called a pre-increment: ++i and a post-increment i++ and there is a difference:
var i = 9;
alert(++i); //-> alerts 10
var j = 9;
alert(j++); //-> alerts 9
alert(j); //-> alerts 10 now, as expected
var k = 9;
alert((k++)); //-> still alerts 9 even with extra parentheses