- Functions are objects
- A Function object contains a string which contains the Javascript code of the function
- For Javascript, the distinction between code and data is sometimes blurred
- One benefit of this function-as-object concept is that you can pass code to another function in the same way you would pass a regular variable or object (because the code is literally just an object)
function some_function2(url, callback) {
var httpRequest; // create our XMLHttpRequest object
if (window.XMLHttpRequest) {
httpRequest = new XMLHttpRequest();
} else if (window.ActiveXObject) {
// Internet Explorer is stupid
httpRequest = new
ActiveXObject("Microsoft.XMLHTTP");
}
httpRequest.onreadystatechange = function() {
// inline function to check the status
// of our request
// this is called on every state change
if (httpRequest.readyState === 4 &&
httpRequest.status === 200) {
callback.call(httpRequest.responseXML);
// call the callback function
}
};
httpRequest.open('GET', url);
httpRequest.send();
}
// call the function
some_function2("text.xml", function() {
console.log(this);
});
console.log("this will run before the above callback");
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