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JavaScript

Posted by Peng-Wen Lai
Peng-Wen Lai
Courses Plus Student 595 Points

I can't get the function part..

function getRandomNumber( upper ){ var num = Math.floor(Math.random() * upper) + 1; return num; }

I can't get: 1) why we don't need to define upper using var? 2) can somebody explain the Math.floor(Math.random() * upper) + 1; return num;
this part?

Thanks!!

1 Answer

Chyno Deluxe
Chyno Deluxe
16,936 Points
Chyno Deluxe
Chyno Deluxe
16,936 Points

1) the parameter upper is the variable name so you wouldn't have to declare it as anther variable.

2) the line of code below explained

/**
 * return a random number between 0 and upper
 * @param  { Number } upper - max number possible
 * @return { Number } - Random number between 0 and upper
 */
getRandomNumber( upper ) {
  var num = Math.floor( Math.random() * upper ) + 1;
  return num;
}

/*
 * (Math.random() * upper) + 1
 * ========================-
 * Math.random() - returns a floating number 
 * between 0 and 1 but will never return 1
 * 
 * multiplying random number by upper
 * sets max returned random number
 *
 * adding + 1 will allow upper 
 * number to be returned
 *
 * Math.floor() - will convert a floating integer
 * into a rounded number
 * 
 */

I hope this helps.