SOURCE

/**
 * @param {number} n
 * @return {string[]}
 */
var generateParenthesis = function(n) {
  let str = 1.0.toFixed(n).substr(2).replace(/0/g, '(') 
  let result = []
  //console.log(str, _case)
  let num = n //剩下的
  var times = 0
	// 递归index，循环num
  function insert(_case, index, num) {
    console.log('index', index)
    num = num > index+1 ? index+1 : num
    // console.log( _case ,'_case')
    times++
    if(times>100){
      return
    }
		
		if(num == 0){
			_case = _case.concat([""])
		}
    for (var i = 0; i < n; i++) {
      // console.log(i,'I')      
      if (num == 0) {
        _case = _case.concat([""])
      } else {
        _case = _case.concat([str.substr(0, i)])
      }
			
    }
		
		if (index <= 0) {
			result.push(_case)
		}
  }

  
  insert([], n-1, num)
  return result
}

try {
  console.log(generateParenthesis(5))
} catch(e) {
  console.log(e)
}