How to copy a HTML tag parameter value into another parameter of the same tag (for every tag in the source text)?

Question 1

I would simply use a regex search & replace on the HTML file for this.

Given input...

<html>
  <head>
    <title>Whatever</title>
  </head>
  <body>
    <form>
      <input name="foo"/>
      <input name="bar"/>
      <input name="foo-bar"/>
    </form>
</html>

..., a regex search on...

name="([a-zA-Z\-]+)"

... and replacement with...

name="$1" id="$1"

...would yield:

<html>
  <head>
    <title>Whatever</title>
  </head>
  <body>
    <form>
      <input name="foo" id="foo"/>
      <input name="bar" id="bar"/>
      <input name="foo-bar" id="foo-bar"/>
    </form>
</html>

The above regex search & replace values use .NET's regex syntax, but they are easily adaptable to Java regex syntax or another regex syntax.

Actually, using the RegexPlanet Java regex tester, I confirmed that the above regex search & replace values should work as-is with an editor or other tool that supports Java regex syntax too.

Question 2

You can use javascript to achieve this: Something like this should work

<html>
<head>
<script type="text/javascript">
**function loadId() { 
var inputs = document.getElementsByTagName('input');
for (var i = 0, len = inputs.length; i < len; i++) {
inputs[i].id = inputs[i].name;
}
}**
</script>
</head>
<body onload="loadId()">
<input name = "test1" /> 
<input name = "test2" /> 
<input name = "test3" /> 

</body>
</html>

Question 3

If your HTML is XHTML (well-formed) (or if you can convert it into XHTML using JTidy, for example), you can use a XSLT transformation to copy the contents of the name attributes into new id attributes.

This stylesheet:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    version="1.0">

    <xsl:output method="html" indent="yes"/>

    <xsl:template match="@*">
        <xsl:attribute name="{name()}">
            <xsl:value-of select="."/>
        </xsl:attribute>
    </xsl:template>

    <xsl:template match="*">
         <xsl:copy>
             <xsl:apply-templates select="*|@*|text()"/>
         </xsl:copy>
    </xsl:template>

    <xsl:template match="input">
        <xsl:copy>
            <xsl:attribute name="id">
                <xsl:value-of select="@name" />
            </xsl:attribute>
            <xsl:apply-templates select="@*" />
        </xsl:copy>
    </xsl:template>
</xsl:stylesheet>

Will convert a file with this content:

<form>
    <div class="inputs">
        <p style="color:red">Text</p>
        <input type="text" name="a" />
        <input type="password" name="b" />
        <input type="checkbox" name="c" />
        <input type="radio" name="d" />
    </div>
</form>

Into this (adds a new id attribute to each input with the contents of the name attribute):

<form>
   <div class="inputs">
      <p style="color:red">Text</p>
      <input id="a" type="text" name="a">
      <input id="b" type="password" name="b">
      <input id="c" type="checkbox" name="c">
      <input id="d" type="radio" name="d">
   </div>
</form>

You can run a XSLT processor using command line tools line Saxon.

Question 4

You can try this:

$("form#myForm :input").each(function(){
    var input = $(this); 
    input.attr('id', input.attr('name'));
});

Haven't tested, but guess should work.