函数中的变量
函数中的变量
提问于 2013-01-25 19:57:39
问题出在变量和函数的返回上。此代码有助于连接到mysql数据库并选择两个城市之间的距离。Variable ret_pomoc是距离。
例如，在another_fuction()中，我需要在另一个函数中使用ret_pomoc中的值。
下面是代码：
var ret_pomoc;
var vzdialenost;
function ajaxFunction(mesto_1,mesto_2){
var ajaxRequest; // The variable that makes Ajax possible!
try{
// Opera 8.0+, Firefox, Safari
ajaxRequest = new XMLHttpRequest();
}catch (e){
// Internet Explorer Browsers
try{
ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
}catch (e) {
try{
ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
}catch (e){
// Something went wrong
alert("Your browser broke!");
return false;
}
}
}
// Create a function that will receive data
// sent from the server and will update
// div section in the same page.
ajaxRequest.onreadystatechange = function(){
if(ajaxRequest.readyState == 4){
var ajaxDisplay = document.getElementById('mapa2');
ajaxDisplay.value = ajaxRequest.responseText;
ret_pomoc=ajaxDisplay.value; //HERE IS KEY VARIABLE
console.log(ret_pomoc); // 1. Here it is OK show 91
}
}
console.log(ret_pomoc); // 2. Here it does not work show undefined and return does not work
// Now get the value from user and pass it to
// server script.
var z_mesta = mesto_1;
var do_mesta = mesto_2;
var queryString = "?z_mesta=" + z_mesta ;
queryString += "&do_mesta=" + do_mesta;
ajaxRequest.open("GET", "pristup.php" +
queryString, true);
ajaxRequest.send(null);
} 我需要在其他函数中使用来自ret_pomoc的值
function another_function(){
vzdialenost=ajaxFunction('Bratislava','Nitra') + ajaxFunction('Poprad','Nitra') ;
}回答 1
Stack Overflow用户
发布于 2013-01-25 20:02:44
ajax请求异步工作，因此实现此目的的方法是传递一个callback函数，该函数将在响应返回时被调用。
Understanding callback functions in Javascript
function some_function2(url, callback) {
var httpRequest; // create our XMLHttpRequest object
if (window.XMLHttpRequest) {
httpRequest = new XMLHttpRequest();
} else if (window.ActiveXObject) {
// Internet Explorer is stupid
httpRequest = new
ActiveXObject("Microsoft.XMLHTTP");
}
httpRequest.onreadystatechange = function() {
// inline function to check the status
// of our request
// this is called on every state change
if (httpRequest.readyState === 4 &&
httpRequest.status === 200) {
callback.call(httpRequest.responseXML);
// call the callback function
}
};
httpRequest.open('GET', url);
httpRequest.send();
}
// call the function
some_function2("text.xml", function() {
console.log(this);
});
console.log("this will run before the above callback");页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/14521360
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