abstract
/
测试.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>

</body>
<script>
    let nums = [2,7,11,15]
    let target = 9
const twoSum = (nums, target) => {
  const prevNums = {};
  for (let i = 0; i < nums.length; i++) {// 存储出现过的数字，和对应的索引
         // 遍历元素
    const curNum = nums[i];                     // 当前元素
    const targetNum = target - curNum;          // 满足要求的目标元素
    const targetNumIndex = prevNums[targetNum]; // 在prevNums中获取目标元素的索引
    if (targetNumIndex !== undefined) {         // 如果存在，直接返回 [目标元素的索引,当前索引]
      return [targetNumIndex, i];
    } else {                                    // 如果不存在，说明之前没出现过目标元素
      prevNums[curNum] = i;                     // 存入当前的元素和对应的索引
    }
  }
}
twoSum(nums,target)
</script>
</html>