Ajax achieves second-level urban linkage (2) and ajax achieves city Linkage

Ajax achieves second-level urban linkage (2) and ajax achieves city Linkage

In the previous article, only ajax requests were obtained and rendered for cities. Here, the provinces are also rendered using ajax requests.

1. HTML

<Select id = "province"> <option> select </option> </select> <select id = "city"> <option> select </option>/ select>

2. JS

/** Province information and city information are all from the server side ** first approach-based on the previous case ** to obtain province information, use an Ajax asynchronous request ** Based on province information, use Ajax asynchronous requests again ** the second approach-rethink ** one-time acquisition of provinces and cities * //. create the XMLHttpRequest object var xhr = getXhr (); // first thought-based on the previous case // 1. when the page is loaded, implement Ajax asynchronous request-province information window. onload = function () {// B. establish a connection-open ("get", "07_province.php"); xhr. open ("get", "07_province.php"); // c. send request-send (null) xhr. send (null); // d. receive data from the server xhr. onreadys Tatechange = function () {if (xhr. readyState = 4 & xhr. status = 200) {var data = xhr. responseText; // converts a string to an array var provinces = data. split (","); // traverse the array for (var I = 0; I <provinces. length; I ++) {// create the option element and add it to the var option = document. createElement ("option"); var text = document. createTextNode (provinces [I]); option. appendChild (text); var province = document. getElementById ("province"); province. AppendChild (option) ;}}}; // 2. when you select province information, implement Ajax asynchronous request-city information var province = document. getElementById ("province"); province. onchange = function () {// clear var city = document. getElementById ("city"); var opts = city. getElementsByTagName ("option"); for (var z = opts. length-1; z> 0; z --) {city. removeChild (opts [z]);} if (province. value! = "Select") {xhr. open ("post", "07_cities.php"); xhr. setRequestHeader ("Content-Type", "application/x-www-form-urlencoded"); xhr. send ("province =" + province. value); xhr. onreadystatechange = function () {if (xhr. readyState = 4 & xhr. status = 200) {var data = xhr. responseText; var cities = data. split (","); for (var I = 0; I <cities. length; I ++) {var option = document. createElement ("option"); var text = document. createTextNode (cities [I]); option. appendChild (text); city. appendChild (option) ;}}}}; // defines the function getXhr () {var xhr = null for obtaining the Ajax core object; if (window. XMLHttpRequest) {xhr = new XMLHttpRequest ();} else {xhr = new ActiveXObject ("Microsoft. XMLHttp ");} return xhr ;}

3. province. php

<? Php echo 'shandong province, Liaoning Province, Jilin Province ';?>

Cities. pnp

<? Php // data used to process the second-level Association of client requests // 1. receive province information sent by the client $ province =$ _ POST ['province ']; // 2. determine the current province information and provide different city information switch ($ province) {case 'shandong province ': echo 'qingdao, Jinan, Weihai, Rizhao, Dezhou'; break; case 'liaoning province ': echo 'shenyang city, Dalian city, Tieling City, Dandong City, Jinzhou City'; break; case 'Jilin province ': echo 'changchun city, Songyuan City, Jilin City, Tonghua City, Siping City '; break;} // is the response string from the server?>

The above is all the content of this article. I hope it will be helpful for your learning and support for helping customers.