[removed] Forloop Difference between i++ and (i+1)

Question

I was building a javascript for loop and I want to compare the value of an array to the next value in the array.

If both values are not equal, I want to return true,

Answer 1

Quite simply, the indexes are the same in this expression:

if(sortedLetters[i] !== sortedLetters[i++]) return true;

If the for loop counter is at 3, for example, it will evaluate sortedLetters[3] !== sortedLetters[3] before incrementing the value.

Using i++ in your for loop will also double-increment your counter.

Answer 2

The i++ is using post increment, so the value of the expression i++ is what the value was in the variable i before the increment. This code:

if(sortedLetters[i] !== sortedLetters[i++]) return true;

does the same thing as:

if(sortedLetters[i] !== sortedLetters[i]) return true;
i = i + 1;

As x !== x always is false for any stable value of x, the code does the same thing as:

if(false) return true;
i = i + 1;

You can use the pre increment version ++i, but if you increment the variable in the statement, you shouldn't increment it in the loop also:

for (i = 0; i < sortedLetters.length; ) {
  if (sortedLetters[i] !== sortedLetters[++i]) return true;
}