random

Math.random()

returns a random number between 0 (inclusive),  and 1 (exclusive) 

回傳0(含)到1(不含)之間的浮點數。

// Returns a random integer from 0 to 9:

Math.floor(Math.random() * 10); 

隨機抽簽，1到9號，4個不重複

function getRandomNumbers(count) {

    const numbers = [];

    //清除陣列

    while (numbers.length>0){

      numbers.pop();

    }

    console.log(numbers);

    //隨機取值丟入陣列

    while (numbers.length < count) {

      const randomNum = Math.floor(Math.random() * 9) + 1;

      if (!numbers.includes(randomNum)) {

        numbers.push(randomNum);

      }

    }

    console.log(numbers);

    sortNumbers(numbers);

    document.getElementById("number").textContent = numbers[0].toString()+numbers[1].toString()+numbers[2].toString()+numbers[3].toString();

  }

  function sortNumbers(numbers){

    for(var i=0;i<3;i++){

      for(var j=i;j<4;j++){

        if(numbers[j]<numbers[i]){

          var t = numbers[i];

          numbers[i] = numbers[j];

          numbers[j] = t;

        }

      }

    }

  }