SOURCE

/*" 
	hi how are you i am fine thank you youtube am am "，
	统计"you"出现的次数
*/
function wordCount(str, word) {
  let arr = str.split(' ') 
  let count = 0
  for (let i of arr) {
    i === word ? count ++ : count
  }
  console.log(count)  //2
  return count
}
wordCount('hi how are you i am fine thank you youtube am','you')


/*" 
	hihowareyouiamfinethankyouyoutubeamam"，
	统计"you"出现的次数
  没有空格
*/

function wordCount2(str, word) {
  let ix = str.indexOf(word)
  let count = 0
  while (ix !== -1) {
    count ++
    str = str.substr(ix + word.length)
    ix = str.indexOf(word)
  }
  console.log(count) //3 youtube
  return count
}
wordCount2('hihowareyouiamfinethankyouyoutubeamam', 'you')