Question

I’m trying to prevent user from inserting * in a textbox.
This is what I was trying to do, but here it only detects * if this is the only inserted character. For example texts like: *, etc.
When allowed characters are mixed with *, then it cannot detect it. For example inputs such as: *hjh, etc..
and maybe how to make it replace only * with “” and not the whole field?

<script type="text/javascript">
    function testField(field) {
        var regExpr = new RegExp("[^*]");
        if(!regExpr.test(field.value)) {
            field.value = "";
        }
    }
</script>

<input type="text" id="searchGamesKeyword" class="searchGamesTextBox"
name="searchGamesKeyword" onblur="testField(this);" />

Answer 1

How about this:

function testField(field) {
    field.value = field.value.replace(/\*/g,"");
}

Called from onblur=testField(this) as shown in the question it will take the current value of the field and replace any and all asterisks with an empty string, leaving all other characters untouched. So, e.g., "ab*cde*" would become "abcde".

The g on the end of /\*/g is a flag meaning to match globally – without this flag it would just replace the first match.

The reason your code didn’t work is that your regex of [^*] will match (i.e., return true from .test()) if there is a non-asterisk character anywhere in the string.