Posts - Page 5 - Philip Ackermann

Neues Node.js-Buch

July 2016

Create a function that only executes once

July 2016

Return after calling a callback

July 2016

Check type of callback parameter

Problem

You want to be sure that the value passed as the callback parameter is really a function.

Ingredients

the typeof operator
the === operator
optional: the toString() and the call method

Directions

Given: a function that accepts a callback function.

function someFunction(callback) {
  callback();
}

July 2016

Create a delaying function in promise-style

Problem

You want to create a function that creates a promise that delays for a given number of milliseconds.

Ingredients

a function
the Promise object
the setTimeout() function

Directions

Create a function that accepts the number of milliseconds.
```
function delay(ms) {
  ...
}
```

July 2016

Create a generic function for partial application

Problem

You want to create a generic function, that produces for a given function the partial applied function.

Ingredients

2 functions
the apply() method
the slice() method

Directions

Define a function that accepts another function (the one that should be partial applicable).
```
function partial(fn /*, args...*/) {
  ...
}
```