continuations

readme.md

@@ -20,6 +20,7 @@ __Table of Contents__
 * [Currying](#currying)
 * [Auto Currying](#auto-currying)
 * [Function Composition](#function-composition)
+* [Continuation](#continuation)
 * [Purity](#purity)
 * [Side effects](#side-effects)
 * [Idempotent](#idempotent)
@@ -175,6 +176,37 @@ const floorAndToString = compose((val) => val.toString(), Math.floor) // Usage
 floorAndToString(121.212121) // '121'
 ```
 
+## Continuation
+
+At any given point in a program, the collection of instructions that still need to be processed in order for the program to complete is known as a continuation.
+
+```js
+const printAsString = (num) => console.log(`Given ${num}`)
+
+const addOneAndContinue = (num, cc) => {
+  const result = num + 1
+  cc(result)
+}
+
+addOneAndContinue(2, printAsString) // 'Given 3'
+```
+
+Continuations are often seen in asynchronous programming when the program needs to wait to receive data before it can continue. The response is often passed off to the rest of the program, which is the continuation, once it's been received.
+
+```js
+const continueProgramWith = (data) => {
+  // Continues program with data
+}
+
+readFileAsync('path/to/file', (err, response) => {
+  if (err) {
+    // handle error
+    return
+  }
+  continueProgramWith(response)
+})
+```
+
 ## Purity
 
 A function is pure if the return value is only determined by its