running if and else within a for loop across columns

I am attempting to have R read across columns by row and evaluate whether values from two adjacent cells are equal. If the values are equal, I want R to count this occurence in a new variable. Here is example data (df):

Var1	Var2	Var3
2	3	3
3	3	3
1	2	3
3	2	1

...and I want to get here:

Var1	Var2	Var3	NewVar
2	3	3	1
3	3	3	2
1	2	3	0
3	2	1	0

One example set of code I have tried out is the following:

df$NewVar <- 0

for (i in 1:2){
  if (df[i]==df[i+1]){
    df$NewVar <- df$NewVar + 1
  }
  else{
    df$NewVar <- df$NewVar
  }
}

This particular set of code just returns 0s in the NewVar variable.

Any sort of help would be much appreciated!