|  | // Hash lookup table as defined by Ken Perlin.  This is a randomly | 
        
          |  | // arranged array of all numbers from 0-255 inclusive. | 
        
          |  | const permutation = [ 151,160,137,91,90,15, | 
        
          |  | 131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23, | 
        
          |  | 190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33, | 
        
          |  | 88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166, | 
        
          |  | 77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244, | 
        
          |  | 102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196, | 
        
          |  | 135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123, | 
        
          |  | 5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42, |