Entry
How will I know if a certain element in a form exists given the element name?
Feb 19th, 2002 01:53
suresh kc, Jo Chua, Suresh KC
Say you were looking for a form element "field1"
you could well.. use a function where you can either go through all
the form objects and check for the one you are looking for like this
//where x is the name of the form
for (o in document.x) {
if(o == "field1")
alert(o +" found");
}
OR
you could directly try to evaluate that element, if it exists
it will return an object otherwise it will return undefined
var exists = eval(document.x["field1"]);
if(exists)
alert("true");
}
sample html file
----------------
<html>
<script language="Javascript">
function e(){
//first way
for (o in document.x)
if(o == "field1")
alert(o +" found");
//second way
var exists = eval(document.x["field1"]);
if(exists)
alert("true");
//second way is more efficient
//the first way is sequential
//second is random access
}
</script>
<body onload=e();>
<form name=x>
<input type=text name=field1>
</form>
</html>
