Math.random();              // returns a random number 

 Math.floor(Math.random() * 10);     // returns a number between 0 and 9 

 Math.floor(Math.random() * 11);      // returns a number between 0 and 10 

 Math.floor(Math.random() * 100);     // returns a number between 0 and 99 

 Math.floor(Math.random() * 101);     // returns a number between 0 and 100 

 Math.floor(Math.random() * 10) + 1;  // returns a number between 1 and 10 

 Math.floor(Math.random() * 100) + 1; // returns a number between 1 and 100 

function getRndInteger(min, max) {
    return Math.floor(Math.random() * (max - min) ) + min;
}

function getRndInteger(min, max) {
    return Math.floor(Math.random() * (max - min + 1) ) + min;
}