solution.js

// description: https://leetcode-cn.com/explore/interview/card/top-interview-questions-easy/8/sorting-and-searching/53/
// 第一个错误的版本

/**
 * Definition for isBadVersion()
 *
 * @param {integer} version number
 * @return {boolean} whether the version is bad
 * isBadVersion = function(version) {
 *     ...
 * };
 */

/**
 * @param {function} isBadVersion()
 * @return {function}
 */
var solution = function(isBadVersion) {
  /**
   * @param {integer} n Total versions
   * @return {integer} The first bad version
   */
  return function(n) {
    var low = 0;
    var high = n - 1;
    var mid;
    while (low < high) {
      mid = Math.floor((high - low) / 2) + low;
      if (isBadVersion(mid)) {
        high = mid - 1;
      } else {
        low = mid + 1;
      }
    }
    return isBadVersion(low) ? low : low + 1;
  };
};