<label for="text1">Text 1</label>
<input type="text" class="text1"  value="To clear"><br>

<label for="text2">Text 2</label>
<input type="text" class="text2" value="to select"><br>

<label for="text3">Text 3</label>
<input type="text" class="text3" value="Click in this field">

<script>
    function myFunction(text3){
        document.text1.value="";
    }
</script>