The compound assignment operators combine an arithmetic operator with an assignment operator.

Here are some prototypes:

varA += varB 
varA -= varB 
varA *= varB 
varA /= varB 

Here are some examples:

var x = 6 
x += 2  //x is equal to 8  
x -= 2  //x is equal to 4  
x *= 2  //x is equal to 12  
x /= 2  //x is equal to 3