JavaScript手动实现JSONP代码

<script>

function removeScript(scriptId) {
  const script = document.getElementById(scriptId);
  document.getElementsByTagName(‘head‘)[0].removeChild(script);
}


function clearFunction(functionName) {
  try {
    delete window[functionName]; //IE8下直接删除会报错
  } catch (e) {
    window[functionName] = undefined;
  }
}

function call(url) {
    var callbackFunction = Math.ceil(Math.random() * 100000 );
    url += (url.indexOf(‘?‘) === -1) ? ‘?‘ : ‘&‘;
    var jsonpScript = document.createElement(‘script‘);
    jsonpScript.setAttribute(‘src‘, `${url}callabck=${callbackFunction}`);
    jsonpScript.id = scriptId;
    document.getElementsByTagName(‘head‘)[0].appendChild(jsonpScript);

    window[callbackFunction] = function(data) {
        //在这里处理数据，然后最后记得一定要删除script并且将函数从window对象上删除掉。 
　　     //Handling data...   
        removeScript(scriptId);
        clearFunction(callbackFunction);
    }
}

</script>