beforecb

beforecb

Wrap a function to call a function before its callback is called

Usage

You can do the following without having to insert code into the function or wrap every call

• Time async functions
• Output when your program is entering / exiting functions

var beforecb = require("beforecb");

var wrapped = beforecb(options, function original, function beforeCbFunction);

Arguments:

• options - Optional - An object with any of the following options:
  • async - the first argument to beforeCbFunction will be a callback and your original callback will only be called once this is called
  • allArgs - arguments to the original function are passed as an array to the first argument of beforeCbFunction
• original - The function you want to wrap.
• beforeCbFunction - A function to call just before the wrapped functions callback.

API Info

• beforecb returns a new function
• You can pass multiple arguments to it, the last function will be presumed to be the callback.
• All arguments to the callback will be passed to the beforecb function.
• By default the original callback is called after beforeCbFunction has returned (If options.async is not set)
• When in async mode all arguments are added as the property args on the callback passed to the beforeCbFunction argument

Examples

var beforefn = require("beforefn"); // https://github.com/timoxley/beforefn
var beforecb = require("../"); 

function slowFunc(callback) {
    for (var i = 0; i < 10e7; i++) {}
    callback();
}

// Time calls to this function without inserting any new code into the function or wrapping calls to it
// Warning: This won't work if you call slowFunc multiple times in parallel.
var startTime;
slowFunc = beforefn(slowFunc, function() {
    startTime = Date.now();
});
slowFunc = beforecb(slowFunc, function() {
    console.log("Total time: " + (Date.now() - startTime));
});

// Call the function as usual, and see timings added
slowFunc(function() {
    console.log("done");
});

See Also

• timoxley/beforefn
• timoxley/afterfn