How do I wrap a function in Javascript?

Question

I\'m writing a global error handling \"module\" for one of my applications.

One of the features I want to have is to be able to easily wrap a function with a t

Answer 1

The following wrapping utility takes a function and enables the developer to inject a code or wrap the original:

function wrap(originalFunction, { inject, wrapper } = {}) {

    const wrapperFn = function(...args) {
        if (typeof inject === 'function') {
            inject(originalFunction, this);
        }
        if (typeof wrapper === 'function') {
            return wrapper(originalFunction, this, args);
        }
        return originalFunction.apply(this, args);
    };

    // copy the original function's props onto the wrapper
    for(const prop in originalFunction) {
      if (originalFunction.hasOwnProperty(prop)) {
        wrapperFn[prop] = originalFunction[prop];
      }
    }
    return wrapperFn;
}

Usage example:

// create window.a()
(function() {

    const txt = 'correctly'; // outer scope variable
    
    window.a = function a(someText) { // our target
        if (someText === "isn't") {
            throw('omg');
        }
        return ['a', someText, window.a.c, txt].join(' ');
    };
    
    window.a.c = 'called'; // a.c property example
})();

const originalFunc = window.a;
console.log(originalFunc('is')); // logs "a is called correctly"

window.a = wrap(originalFunc);
console.log(a('is')); // logs "a is called correctly"

window.a = wrap(originalFunc, { inject(func, thisArg) { console.log('injected function'); }});
console.log(a('is')); // logs "injected function\na is called correctly"

window.a = wrap(originalFunc, { wrapper(func, thisArg, args) { console.log(`doing something else instead of ${func.name}(${args.join(', ')})`); }});
console.log(a('is')); // logs "doing something else instead of a(is)"

window.a = wrap(originalFunc, {
    wrapper(func, thisArg, args) {
        try {
            return func.apply(thisArg, args);
        } catch(err) {
            console.error('got an exception');
        }
    }
});
a("isn't"); // error message: "got an exception"

The last example demonstrates how to wrap your function with a try-catch clause