for循环中的Ajax请求(Ajax request in for loop)

我想用for循环循环100次ajax请求。 这是我的代码：

for(var i=1; i<100; i++)

{

var num = i+1;

var request = new XMLHttpRequest();

request.open("GET", "http://localhost/test/1/2/main.php?t="+num+"", true);

request.send(null);

request.onreadystatechange = function() {

if (request.readyState == 4) {

var parser = new DOMParser();

var doc = parser.parseFromString(request.responseText, "text/html");

var rows = doc.getElementsByTagName("table")[0].getElementsByTagName("tbody")[0].getElementsByTagName("tr");

var sum = 0;

for(var j=0; j

{

sum += parseInt( rows[j].getElementsByTagName("td")[7].textContent.trim() );

}

alert(num);

}

}

}

但它不起作用。 在控制台中，我看到100次此信息：

等等一切都应该没问题。 但我只看到警报14次(我现在不知道为什么14次)，没有100次。

为什么这个程序不起作用？

I'd like to loop 100 times ajax request with for loop. This is my code :

for(var i=1; i<100; i++)

{

var num = i+1;

var request = new XMLHttpRequest();

request.open("GET", "http://localhost/test/1/2/main.php?t="+num+"", true);

request.send(null);

request.onreadystatechange = function() {

if (request.readyState == 4) {

var parser = new DOMParser();

var doc = parser.parseFromString(request.responseText, "text/html");

var rows = doc.getElementsByTagName("table")[0].getElementsByTagName("tbody")[0].getElementsByTagName("tr");

var sum = 0;

for(var j=0; j

{

sum += parseInt( rows[j].getElementsByTagName("td")[7].textContent.trim() );

}

alert(num);

}

}

}

But it's not working. In console I see 100 times this information:

Etc. So everything should be ok. But I see alert only 14 times (I don't now why 14),no 100.

Why this program not working?

原文：https://stackoverflow.com/questions/39269211

更新时间：2020-01-18 15:56

最满意答案

请在下面的代码。 这将允许仅在上一次完成之后触发ajax调用。 所以不会错过任何ajax电话。

var num = 0;

doAjax(0);

function doAjax(arrCount)

{

if(num<100){

num += 1;

var request = new XMLHttpRequest();

request.open("GET", "http://localhost/test/1/2/main.php?t="+num+"", true);

request.send(null);

request.onreadystatechange = function() {

if (request.readyState == 4) {

var parser = new DOMParser();

var doc = parser.parseFromString(request.responseText, "text/html");

var rows = doc.getElementsByTagName("table")[0].getElementsByTagName("tbody")[0].getElementsByTagName("tr");

var sum = 0;

for(var j=0; j

{

sum += parseInt( rows[j].getElementsByTagName("td")[7].textContent.trim() );

}

alert(num);

doAjax(num)

}

}

}

}

Please below code. Which will allow to fire ajax call only after previous has been completed. So no ajax call will missed.

var num = 0;

doAjax(0);

function doAjax(arrCount)

{

if(num<100){

num += 1;

var request = new XMLHttpRequest();

request.open("GET", "http://localhost/test/1/2/main.php?t="+num+"", true);

request.send(null);

request.onreadystatechange = function() {

if (request.readyState == 4) {

var parser = new DOMParser();

var doc = parser.parseFromString(request.responseText, "text/html");

var rows = doc.getElementsByTagName("table")[0].getElementsByTagName("tbody")[0].getElementsByTagName("tr");

var sum = 0;

for(var j=0; j

{

sum += parseInt( rows[j].getElementsByTagName("td")[7].textContent.trim() );

}

alert(num);

doAjax(num)

}

}

}

}

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