APPELLER UN WEBSERVICE DEPUIS JAVASCRIPT

function Calculate(txtVal1, txtVal2)
{
    var xhr = createXHR();

    xhr.open("POST", "WebService1.asmx/CalcAddition", true);

    xhr.onreadystatechange = function()
    {
        if (xhr.readyState === 4)
        {
            txtResult.value = xhr.responseXML.text;
        }
    };
    xhr.setRequestHeader("content-type", "application/x-www-form-urlencoded");
    var postData = "val1=" + txtVal1.value + "&val2=" + txtVal2.value;
    xhr.send(postData);

}

function createXHR()
{
    var xhr;

    if (window.XMLHttpRequest)
    {
        // if browser is not IE or is IE >= 7 XMLHttpRequest
        // will be exposed in the window namespace
        xhr = new XMLHttpRequest();
    }
    else if (window.ActiveXObject)
    {
        // if IE < 7 create via ActiveX
        xhr = new ActiveXObject('Microsoft.XMLHTTP');
    }
    else
    {
        throw new Error("Could not create XMLHttpRequest object.");
    }
    return xhr;
}