<<NN 2 IE 3 ECMA 1

The bitwise left-shift operator shifts the bits of the first operand by the number of columns specified by the second operand. For example, if the binary value of 3 (0011) has its bits shifted to the left by 2, the binary result is 1100; the decimal equivalent is 12.

 
Example
 
var shifted = 3 << 2;