How to get returned value of function javascript

Question

I am trying to write my own Xhr wrapper as practice. I am in the process of getting things to work cross browser I came across this piece of code that initiates a xhr object for all browsers IE5.5+

But i personally dont really understand how to now use this instantiated xhr object.

See the code below:

(function () {
    try {
        return new(this.XMLHttpRequest || ActiveXObject)('MSXML2.XMLHTTP.3.0');
    } catch (e) {}
})();

Could someone explain to me how to use the instantiated xhr object?
And maybe for my own learning experience how this (function (){})(); thing works

If something is unclear let me know so I can clarify!

georg · Accepted Answer · 2019-06-07 22:25:10Z

2

Your expression is an IIFE - you define a function and call it right away. Since you don't assign the result to anything, it's lost. So either do

var req = (function () {
    try {
        return new(this.XMLHttpRequest || ActiveXObject)('MSXML2.XMLHTTP.3.0');
    } catch (e) {}
})();

or (more readable)

function getRequest() {
    try {
        return new(this.XMLHttpRequest || ActiveXObject)('MSXML2.XMLHTTP.3.0');
    } catch (e) {}
}

var req = getRequest()

Not sure about all that ActiveXObject stuff though.

answered Jun 7, 2019 at 22:25

georg

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