javascript - var ajaxreq = false,ajaxCallback;
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问题描述
问 题
/**
* ajax库
*/
// global variables to keep track of the request and the function to call when done
var ajaxreq = false,ajaxCallback;
// ajaxRequest: Sets up a request
function ajaxRequest(filename) {
try {
// Firefox /IE7 /Others
ajaxreq = new XMLHttpRequest();
} catch (error) {
try {
// IE5 / IE6
ajaxreq = new ActiveXOject("Microsoft.XMLHTTP");
} catch (error) {
return false;
}
}
ajaxreq.open("GET",filename);
ajaxreq.onreadystatechange = ajaxResponse;
ajaxreq.send(null);
}
// ajaxResponse: Waits for response and calls a function
function ajaxResponse(){
if(ajaxreq.readyState != 4) return;
if(ajaxreq.status == 200) {
// if the request succeed...
if(ajaxCallback) ajaxCallback();
}else alert("Request failed: " + ajaxreq.statusText);
return true;
}
开头的var ajaxreq = false,ajaxCallback;是声明ajaxreq对象吗?ajaxCallback在这个地方是什么意思?初学JavaScript,请前辈指教哈
function ajaxResponse(){
if(ajaxreq.readyState != 4) return;
if(ajaxreq.status == 200) {
// if the request succeed...
if(ajaxCallback) ajaxCallback();
}else alert("Request failed: " + ajaxreq.statusText);
return true;
}
请大神帮忙解释下这个4 和 200吧?还有别的值吗?
解决方案
var ajaxreq = false,ajaxCallback;
只是声明了 两个变量, 形同c语言的 int a=b,c;
ajaxCallback 这里只是声明,实际在用时是个回调,ajaxCallback = function(){//……}
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