function fun() {
if (document.getElementById('001').value == 'ok') {
document.getElementById('002').value = 1;
} else {
document.getElementById('002').value = 2;
}
}
<input type="text" name="001" id="001" value="文本框1" />
<br>
<br>
<input type="text" name="002" id="002" value="文本框2" />
<br>
<br>
<input type="button" name="003" id="003" value="按钮" onclick="fun()" />