https://leetcode-cn.com/problems/two-sum/

    1. function twoSum(nums: number[], target: number): number[] {
    2.   for(let i = 0; i < nums.length; i++) {
    3.     const diff = target - nums[i];
    4.     const j = nums.indexOf(diff);
    5.     if (j > -1 && j !== i) {
    6.       return [i, j];
    7.     }
    8.   }
    9. }
    function compose(){
  //请实现
}
const multiply20 = (price) => price * 20;
const divide100 = (price) => price / 100;
const normalizePrice = (price) => price.toFixed(2);
const discount = compose(normalizePrice, divide100, multiply20);
discount(200.0); //40.00