Question

I need to override (enrich) a Javascript function. Problem is the function is generated automatically:

var original_function = getFunction('someID'); // eval('someID');

My code will be something like this:

var f = function(arg) { 
 do_some_stuff(); 
 original_function(arg);  
 do_another_stuff(); 
} 

And now when other part of code calls getFunction('someID') the f('someID') will be returned.

How to override the original function, when we know it’s name or we have only a function object?

Answer 1

function someFunc (arg) { alert(arg)}


function injectFunc(original, injection, inject_after) {
if(typeof original === "string") original = window[original];
return function() {
    if(!inject_after) injection.apply(this, arguments);
    var result = original.apply(this, arguments);
    if(inject_after) injection.apply(this, arguments);
    return result;
    }
}

// insert before
someFunc = injectFunc(someFunc, function(arg) {alert("Before" + arg)});

// or with string func name
someFunc = injectFunc('someFunc', function(arg) {alert("Before" + arg)});

// and after
someFunc = injectFunc(someFunc, function(arg) {alert("After" + arg)}, true);


// and with olny func name 
window['someFunc'] = injectFunc('someFunc', function(arg) {alert("After" + arg)}, true);

all injections are stored in function