Synchronous proxy

proxy.js

/**
 * 
 * 异步 get 需要回调
**/

let choice = 'a';

let proxyList = [];

function initProxyWayA() {
  // if proxyList comes from request.getAsync. things will get bad.
  proxyList = [
    { address: 'http://192.168.0.1',
     valid: true },
    { address: 'http://192.168.0.1',
     valid: true },
    { address: 'http://192.168.0.1',
     valid: true },
  ];
}

function initProxyWayB() {
  proxyList = [
    { address: 'http://127.0.0.1',
     valid: true },
    { address: 'http://127.0.0.2',
     valid: true },
    { address: 'http://127.0.0.3',
     valid: true },
  ];
}


// 两种方式的选择
function initialProxy() {
  if (choice === 'a') {
    initProxyWayA();
  } else {
    initProxyWayB();
  }
}

// 可用性的检测
function findValidProxyIndex() {
  return proxyList.findIndex((proxy) => proxy.valid);
}


function getSingleProxy() {
  const idx = findValidProxyIndex();
  if (proxyList.length === 0 || idx === -1) {
    initialProxy();
    return proxyList[0].address;
  } else {
    return proxyList[idx].address;
  }
}

console.log(getSingleProxy());