Why can't I use - in field names?
Question
Basically I'm just trying to clear a text field, which has never been a problem for me. However, this is NOT working:
<html>
<body>
<form name="form">
<input type="text" name="input-field" value="Value" />
<input type="button" name="clear" value="Clear field" onclick="document.form.input-field.value = ''"; />
</form>
</body>
</html>
But if I rename "input-field" to "inputfield" and onclick to onclick="document.form.inputfield.value = ''"; ... Then it works fine.
However... Removing the "-" from the field name, is not an option in my case (long explanation).
So, how do I clear a text field, containing a "-"???
2 answers
solution1
10 ACCPTED 2012-09-08 23:49:16
Because it's not a valid JavaScript identifier. However, you can use the following instead:
document.form['input-field'].value
It's for the same reason you can't declare a variable using var my-var . On the other hand, if you have an object , such as form with several keys, you can access its properties as if it was an associative array:
var form = {
"input-field": 20,
otherKey: 30
};
form.input-field; // Error
form.otherKey; // OK
form['input-field']; // OK
References:
- Identifier Names and Identifiers (ECMAScript Language Specification)
- Objects as associative arrays
solution2
6 2012-09-08 23:52:17
- is not a valid character in an identifier because, for example
document.form.input-field;
is interpreted as
document.form.input - field;
Of course you can remedy the problem by using the square bracket notation:
document.form["input-field"];
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