How to get Javascript Function Calls/Trace at Runtime

Question

As I interact with my AJAX based application at RUNTIME I\'d like the console to spit out all the functions it\'s calling. (so no stack trace, or breakpoints, or pr

Answer 1

A variation on Briguy37's solution, I wrote one that accepts a function to call before each method. It also works with ECMAScript 6 classes, where methods are not enumerated by for...in. I'm using it to modify Object prototypes, to add logging to all new instances of my object.

function inject(obj, beforeFn) {
    for (let propName of Object.getOwnPropertyNames(obj)) {
        let prop = obj[propName];
        if (Object.prototype.toString.call(prop) === '[object Function]') {
            obj[propName] = (function(fnName) {
                return function() {
                    beforeFn.call(this, fnName, arguments);
                    return prop.apply(this, arguments);
                }
            })(propName);
        }
    }
}

function logFnCall(name, args) {
    let s = name + '(';
    for (let i = 0; i < args.length; i++) {
        if (i > 0)
            s += ', ';
        s += String(args[i]);
    }
    s += ')';
    console.log(s);
}

inject(Foo.prototype, logFnCall);