Edit in JSFiddle

Array.prototype.forEach.call(document.getElementsByTagName("input"), function(input){
    if (input.type == "button"){
        input.addEventListener("click", function(){
            alert(this.parentNode.parentNode.children[0].innerHTML);
        });
    }
});

<table>
    <tr>
        <th>id</th>
        <th>Nombre</th>
        <th>boton</th>
    </tr>
    <tr>
        <td>1</td>
        <td>Carlos</td>
        <td><input type="button" value = "clic" /></td>
    </tr>
    <tr>
        <td>2</td>
        <td>José</td>
        <td><input type="button" value = "clic" /></td>
    </tr>
    <tr>
        <td>3</td>
        <td>María</td>
        <td><input type="button" value = "clic" /></td>
    </tr>
</table>