I have a problem with making two buttons in my HTML code increase or decrease text when I click on either button. I have what I think is the correct javascript code I just have a problem with the buttons working. Any help with this issue is appreciated.
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<hgroup>
<div id="fontbuttons">
<input type="image" id="fontdown" alt="-" src="fontdown.png" button value="-0.1" />
<input type="image" id="fontup" alt="+" src="fontup.png" button value="0.1" />
window.onload=function(){startup();};
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<h1>Twins and Talking</h1>
<h2>by Peter Kuhlman, M.D., Ph.D.</h2>
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<img src="kuhlman.png" alt="" />
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<p>Communication occurs long before speech. Babies communicate
with their parents through crying, laughter, smiling and
pointing. The attentive parent quickly becomes attuned to
this "non-speech" communication. Usually in the second year of
life, babies will begin to add single words to these acts
of expression. A baby will point to a cup and say, "drink."
The names "Mama" and "Dada" are among the first out of a
baby's mouth.
</p>
<p>As the child gets older, he or she will add new words to
these expressions and will begin to use words in
combination: "get drink me." The parents provide visual
and audio feedback to the child, encouraging the development
of speech. Through a process called echoing, parents
will naturally repeat what their child says, providing an
important confirmation that what the child has said has
been heard and understood.
</p>
<p>With twins, the situation may be slightly different.
Often parents cannot provide the one-to-one feedback that
single children routinely enjoy. It may be that the one
providing most of the feedback is the other twin!
</p>
<p>While the other twin is usually a very attentive and
eager audience, he or she cannot provide the type of
feedback needed for language development. Twins
cannot correct each other's mistakes in the use of words
or grammar. Moreover, by communicating with each other,
twins are necessarily decreasing the amount of communication
with adults and older children. In some cases, twins become
such good audiences for each other, they lose interest
in communicating with their parents!
</p>
<p>In rare cases, this one-to-one communication can progress
to the point at which a shared language is created.
The twins will come up with their own words, and in some
cases, their own grammatical structures. The languages
are unintelligible to anyone else but the twins. These cases
are very rare, even though they are well publicized.
The twin's secret language will usually disappear by age
4 or 5, as they become more adept at using their
parent's language.
</p>
<p>What can you do to help your twins in acquiring
language? The most important thing you can do is pay
individual attention to each child. Easier said than
done! Provide feedback to each child as he or she gropes
with language. If you are feeding your twins, talk to one
child as the other is eating. Then, when the first child
is eating, switch to the second. When changing
diapers, use the one-on-one time (one hopes) to further
provide the audio clues needed for learning language.
</p>
<p>As with everything that is twin-related, language
acquisition requires some extra work on the part of the
parents; but again with twin-related activities,
the extra work is paid off in extra fun.
</p>
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Twin Life Magazine: Issue 189; © 2015 (US)
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JavaScript
function startup() {
var fontButtons = document.getElementsByClassName("fontsizer");
var i;
alert(fontButtons.length);
for (i = 0; i < fontButtons.length; i++) {
fontbuttons[i].onclick = function(){resizeText(this);};
}
function resizeText(ObjectButton) {
var fontChange;
fontChange = parseFloat(objectButton.value);
if (document.body.style.fontSize == "") {
document.body.fontSize = "1.0em";
}
var currentFontSize;
alert("changed");
currentFontSize = parseFloat(document.body.style.fontSize);
currentFontSize = currentFontSize + fontChange;
document.body.style.fontSize = "currentFontSize+em"
}
}
