Js-promise (causes asynchronous operations to execute synchronously)

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It is very convenient to use promise to make asynchronous operations synchronous, and I have been learning for a long time about the use of this promise when I am having a synchronous execution of an indeterminate number of asynchronous operations (at the time because of the lack of understanding and a long struggle), and to summarize, hoping to help everyone

Single Asynchronous Operation synchronization

<div id="box"></div><script>  var box = document.querySelector(‘#box‘)  var p = new Promise(function(resolve, reject){    setTimeout(function(){      box.innerHTML += ‘网络请求<br>‘;      resolve()    }, 1000)  })  p.then(function(resolve){    box.innerHTML += ‘结束<br>

Determining the number of asynchronous Operation Synchronizations

<div id="box"></div><script>  var p = new Promise(function(resolve, reject){    setTimeout(function(){      box.innerHTML += ‘建立连接<br>‘;      resolve(‘ok‘)    }, 1000)  })  function post_sth(data){    return new Promise(function(resolve, reject){      setTimeout(function(){        box.innerHTML += ‘post网络请求,此时data=‘+data+‘ <br>‘;        resolve(data+‘|post‘)      }, 1000)    })  }  function get_sth(data){    return new Promise(function(resolve, reject){      setTimeout(function(){        box.innerHTML += ‘get网络请求,此时data=‘+data+‘ <br>‘;        resolve(data+‘|get‘)      }, 1000)    })  }    p.then(post_sth).then(get_sth).then(post_sth).then(function(data){    box.innerHTML += ‘最后data=‘+data+‘<br>

Indefinite number of asynchronous operation synchronization

<div id="box"></div><script>  var p = new Promise(function(resolve, reject){resolve()})  /**    function      返回function（供本then用）        返回Promise（供下一个then用）  */  function get_request_sth_func(i){    return function request_sth(){      return new Promise(function(resolve, reject){        setTimeout(function(){          box.innerHTML += ‘请求‘+i+‘<br>‘;          resolve()        }, Math.round(Math.random()*1000))      })    }  }  for (var i = 0; i < 20; ++i) {    p = p.then(get_request_sth_func(i))  }  p.then(function(){    box.innerHTML += ‘完成<br>

Js-promise (causes asynchronous operations to execute synchronously)