匹配关键词在字符串中各处出现的位置的索引，组成数组。

indexes.js

// 循环
let find = (str, keyword) => {
  let i = 0, arr = []
  let index = 0
  while (true) {
    index = str.indexOf(keyword, i)
    if (index == -1) break
    arr.push(index)
    i = index + 1
  }
  return arr
}

// 递归
function indexes(string, str) {
  var ret = []
  var from = 0
  var isFin = false
  function inner (string, str) { 
    var index = string.indexOf(str, from)
    if ( index > -1 ) {
      ret.push(index)
      from = index + 1
      inner(string, str)
    }
  }

  inner(string, str)
  return ret 
}

indexOf('1010', '0') // -> [1, 3]

// 尾递归
function indexOf(string, str) {
  var ret = []
  var from = 0
  var isFin = false
  function inner (string, str) { 
    var index = string.indexOf(str, from)
    if ( index > -1 ) {
      ret.push(index)
      from = index + 1
      return inner(string, str)
    } else {
      return ret
    }
  }

  return inner(string, str)
}