Is the condition in the for loop computed in each loop?

Question

I have a situation like:

for(var i = 0; i < a + b; ++i)
  // code that doesn't affect a and b

Do I have to worry about the addition being done at each iteration? Or is JavaScript (its parser?) Smart enough to understand what a + bis a constant?

In other words, should I do this as follows:

var end = a + b;
for(var i = 0; i < end; ++i)
  // code

or will this lead to the cancellation of a line of code?

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Well, actually what I'm worried about is not just one line of code, but the fact that I think about it every time I come across a similar situation in JavaScript! In addition, today it is an addition, tomorrow it may be something else, like the square root of it, so I consider it important!

Answer 1

:

for(var i = 0, end = a + b; i < end; ++i)

---

:

for(var i = a + b; i--;)

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. :

for(var i = 0; i < array.length; ++i) { 
   array.push('value'); // infinite loop
}

array.length , array.push().

Answer 2

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: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for

for ([initialization]; [condition]; [final-expression])
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Answer 3

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