[英]Javascript Event Listener to change paragraph text onclick of button doesn't work?
[英]Problems with Javascript & AJAX - Event Listener for select form doesn't work on change?
我对javascript不太熟悉,我正在建立一个基本网站,有人可以在一个小型汽车数据库中进行搜索,该数据库会在用户选择搜索条件时更新搜索结果。
我试图通过在html中制作一个具有多个选择的表单(代码1)和带有事件侦听器的javascript来进行选择,并通过ajax通过PHP文件搜索数据库(代码2)来实现此目的。
代码1-HTML
<div class="intro">
<p>Enter your search criteria:</p>
<div id="formbox">
<form>
<!-- MAKE SELECTION -->
<select name="make" id="selectmake">
<option value="test">Car Make:</option>
<option value="Aston Martin">Aston Martin</option>
<option value="Ford">Ford</option>
<option value="Lotus">Lotus</option>
<option value="Vauxhall">Vauxhall</option>
</select> 
<!-- MODEL SELECTION -->
<select name="model" id="selectmodel">
<option value="">Car Model:</option>
<option value="DB9 Coupe">DB9 Coupe</option>
<option value="Vanquish">Vanquish</option>
<option value="Fiesta Hatchback">Fiesta Hatchback</option>
<option value="Focus Hatchback">Focus Hatchback</option>
<option value="Mondeo Estate">Mondeo Estate</option>
<option value="Elise">Elise</option>
<option value="Exige">Exige</option>
<option value="Astra Hatchback">Astra Hatchback</option>
<option value="Corsa D">Corsa D</option>
<option value="Frontera 4x4">Frontera 4x4</option>
</select> 
<!-- YEAR SELECTION -->
<select name="year" id="selectyear">
<option value="">Car Year:</option>
<option value="1998">1998</option>
<option value="2000">2000</option>
<option value="2001">2001</option>
<option value="2004">2004</option>
<option value="2007">2007</option>
<option value="2009">2009</option>
<option value="2010">2010</option>
</select> 
<!-- CC SELECTION -->
<select name="cc" id="selectcc">
<option value="">Car CC:</option>
<option value="1250">1250</option>
<option value="1400">1400</option>
<option value="1600">1600</option>
<option value="1800">1800</option>
<option value="2000">2000</option>
<option value="3200">3200</option>
<option value="5900">5900</option>
<option value="6000">6000</option>
</select> 
<!-- COLOUR SELECTION -->
<select name="colour" id="selectcolour">
<option value="">Car Colour:</option>
<option value="Black">Black</option>
<option value="Blue">Blue</option>
<option value="Red">Red</option>
<option value="Silver">Silver</option>
</select> 
<!-- RESET SELECTIONS -->
<input type="reset" />
</form>
</div>
</div>
<!-- SEARCH RESULTS -->
<div id="results">
Your results will be displayed here
</div>
代码2-JAVASCRIPT文件
function initialise() {
//assign selection fields to variables
var i=0;
var make=document.getElementById("selectmake");
make.addEventListener('change', setmake(this.value), false);
var model=document.getElementById("selectmodel");
model.addEventListener('change', setmodel(this.value), false);
var year=document.getElementById("selectyear");
year.addEventListener('change', setyear(this.value), false);
var cc=document.getElementById("selectcc");
cc.addEventListener('change', setcc(this.value), false);
var colour=document.getElementById("selectcolour");
colour.addEventListener('change', setcolour(this.value), false);
//assign results area to a variable
var results=document.getElementById("results");
//setting search criteria to return all results by default
var makesearch="make=make";
var modelsearch="model=model";
var yearsearch="year=year";
var ccsearch="cc=cc";
var coloursearch="colour=colour";
results.innerHTML="initiate works";
//function to set the search to search make if set to an existent value
function setmake (makevar) {
i=i+1;
results.innerHTML=i;
if (makevar.length>0) {
makesearch="make='"+makevar+"'";
results.innerHTML="EVENTIFFUNCTIONworks";
constructsearch();
}
}
function constructsearch() {
var searchstring="WHERE "+makesearch+" AND "+modelsearch+" AND "+yearsearch+" AND "+ccsearch+" AND "+coloursearch;
results.innerHTML="construct works";
sendsearch(searchstring);
}
}
//function to update search results
function sendsearch(searchstring) {
//update search results with an XMLHttpRequest
if (window.XMLHttpRequest) {
// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else {
// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState==4 && xmlhttp.status==200) {
document.getElementById("results").innerHTML="XMLworks";
//xmlhttp.responseText;
}
}
xmlhttp.open("GET","results.php?search="+searchstring,true);
xmlhttp.send();
}
window.onload=initialise;
变量'i'已完成,其所有用途均用于测试...我确实做到了这一点,即在加载页面时,结果div将显示'i'变量,但当在“制造”选择框中进行了新选择。
由于某种原因,我的代码现在根本无法使用,甚至无法显示“启动作品”
非常感谢您的任何帮助,并在此先感谢。
addEventListener
将函数作为第二个参数,因为您没有传递函数而是调用函数。 您可以使用匿名函数表达式来包装对addEventListener
的调用中的代码。 对于您对addEventListener
每个调用,请执行以下操作
make.addEventListener('change', function(){
setmake(this.value)
}, false);
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