Callback pattern when passing method of an object.

main.js

    // Calling callback when callback is a method of an object
    var myapp = {};
    myapp.elementHeight = 100;
    myapp.setElementHeight = function (node) {
        node.style.height = this.elementHeight;
    };
    // Where setElementHeight is our callback

    // findNodes() function which call our callback
    var findNodes = function (callback) {

        if (typeof callback === 'function') {
            // ... find some node
            callback(foundNode)
        }
    };
    // If we call findNodes(myapp.setElementHeight),
    // it won't work as expected, because this.elementHeight will not be defined and 'this' will point to global object.
    // Solution is to pass the callback and to pass the object this callback belongs to.
    findNodes(myapp.setElementHeight, myapp);

    // And adjusted callback caller would be:
    var findNodes = function (callback, callback_obj) {
        // ... find some node
        if (typeof callback === 'function') {

            callback.call(callback_obj, foundNode);
        }
    };
    // If we want to avoid passing the same object twice, we could pass the method as a string.
    findNodes("setElementHeight", myapp);

    // Then the findNodes function would be something like this:
    var findNodes = function (callback, callback_obj) {
        // ... find some node
        if (typeof callback === "string") {
            callback = callback_obj[callback];
        }
        if (typeof callback === "function") {
            callback.call(callback_obj, foundNode);
        }
    }