Javascript select drop down menu onchange not firing properly

问题

my onchange isn't firing the javascript method properly.

Select code (in HTML file)

<select id="crit_1" onchange="crit1Update()">
    <option value=null>Criteria 1</option>
 <option value="major">Major</option>
 <option value="grad">Graduation Year</option>
</select>

crit1Update() code (in external filter.js file in same folder as HTML file containing the above with the following code in head of HTML

<script type="text/javascript" src="filter.js">
</script>

function crit1Update() {
 var crit1 = document.criteria.getElementsByID("crit1");
 var criteria1 = crit1.options[crit1.selectedIndex].value;
 alert("criteria1"); // this is never firing, so this isnt getting called
 if (criteria1 == null) {
  // eventually set all other lists to null in here as well
  filter(null,null,null,null,null,null)
            // the above returns all the resumes 
            // (this is eventually going to filter resumes)
 }
 else if (criteria1 == "major") {
  alert("Major!");
 }
}

Are there any glaring or not glaring errors that I am missing? I dont see why the alert("criteria1" isnt being called. I come from a java background and this is my first foray into JS, so I may be missing something simple.

Thanks for any help.

回答1:

Your <select> ID is "crit_1" and your function is looking for ID "crit1" (no underscore).

It would probably be a better idea to pass the <select> element as a reference to the function, eg

JavaScript

function crit1Update(crit1) {
    var criteria1 = crit1.options[crit1.selectedIndex].value;

HTML

<select id="crit1" name="crit1" onchange="crit1Update(this)">

回答2:

There is a typo in this method call:

document.criteria.getElementsByID(

should be

document.criteria.getElementById(
                            ^  ^ no "s" and lower case "d"

also make sure the id matches your HTML element e.g. "crit_1"

来源：https://stackoverflow.com/questions/4048406/javascript-select-drop-down-menu-onchange-not-firing-properly

标签

javascript

onchange