[65] 有效数字

/**
 * @param {string} s
 * @return {boolean}
 */
var isNumber = function (s) {
  const graph = {
    0: { 'blank': 0, '.': 2, 'digit': 6, 'sign': 1 },
    1: { 'digit': 6, '.': 2 },
    2: { 'digit': 3 },
    3: { 'digit': 3, 'e': 4, 'E': 4 },
    4: { 'digit': 5, 'sign': 7 },
    5: { 'digit': 5 },
    6: { 'digit': 6, '.': 3, 'e': 4, 'E': 4 },
    7: { 'digit': 5 }
  };

  let state = 0;

  for (c of s.trim()) {
    //转换字符
    if (c >= 0 && c <= 9) {
      c = 'digit'
    } else if (c === ' ') {
      c = 'blank'
    } else if (c === '+' || c === '-') {
      c = 'sign';
    }
    //切换状态
    state = graph[state][c]
    if (state === undefined) {
      return false
    }
  }
  if (state === 3 || state === 6 || state === 5) {
    return true
  }
  return false
};