javascript - 无法访问数组元素。将一个 ajax 请求的结果用于另一个 ajax 请求

Question

    //global variables
var corpArray = new Array(); //store corp classes instances
var corpId = new Array(); //store corp id's

window.onload = init();

function init() {
  getNpcCorpId();
  console.log(corpId);
  getCorpNames(corpId[5]);
}

//get all corporation id's from the game
function getNpcCorpId() {
  let conName = new XMLHttpRequest();
  conName.onload = function() {
    if (this.status == 200) {
      let idList = JSON.parse(this.responseText);
      idList.forEach(element => {
        corpId.push(element);
      });
    }
  };
  conName.open(
    "get",
    "https://esi.evetech.net/latest/corporations/npccorps/?datasource=tranquility",
    true
  );
  conName.send();
}

//get corporation name
function getCorpNames(element) {
  console.log(element);
  let corpConn = new XMLHttpRequest();
  corpConn.onload = () => {
    if (this.status == 200) {
      console.log(this.responseText);
    }
  };
  corpConn.open(
    "get",
    `https://esi.evetech.net/latest/corporations/${element}/?datasource=tranquility`,
    true
  );
  corpConn.send();
}

我正在尝试创建一个 eve 在线 api，我想使用 2 个全局变量来存储我检索到的值(因为我不知道另一种方式)我将使用几个函数来使用提供的 eve api。我可以无法访问我的 corpId 单个元素，当我控制台记录我的所有数组时，一切正常，但是当我想访问单个元素时，它似乎不安全。

Answer 1

 //global variables
var corpArray = new Array(); //store corp classes instances
var corpId = new Array(); //store corp id's

window.onload = init();

async function  init() {
  await getNpcCorpId();
  console.log(corpId);
  getCorpNames(corpId[5]);            // asynchronous behaviour - let it be fix using await and async
}

//get all corporation id's from the game
function getNpcCorpId() {
	return new Promise(function(resolve, reject) {
		let conName = new XMLHttpRequest();
		conName.onload = function() {
			if (this.status == 200) {
			  let idList = JSON.parse(this.responseText);
			  idList.forEach(element => {
				corpId.push(element);
			  });
			}
			resolve();
		};
  conName.open(
    "get",
    "https://esi.evetech.net/latest/corporations/npccorps/?datasource=tranquility",
    true
  );
  conName.send();
	
});

  
}

//get corporation name
function getCorpNames(element) {
  console.log(element);
  let corpConn = new XMLHttpRequest();
  corpConn.onload = () => {
    if (this.status == 200) {
      console.log(this.responseText);
    }
  };
  corpConn.open(
    "get",
    `https://esi.evetech.net/latest/corporations/${element}/?datasource=tranquility`,
    true
  );
  corpConn.send();
}

This is due to asynchronous behaviour - in simple terms - when you call getNpcCorpId() it is a http request it will take some time to execute but next line run immediately so at that point of time corpId is still blank. So to fix this issue you can use await that will makes JavaScript wait until the promise returns a result.

希望对你有帮助!