diff --git a/functional-programming.js/cachable-function.js b/functional-programming.js/cachable-function.js
new file mode 100644
index 0000000..e116902
--- /dev/null
+++ b/functional-programming.js/cachable-function.js
@@ -0,0 +1,28 @@
+const sleep = (milliseconds) => {
+    const end = Date.now() + milliseconds
+    while (Date.now() < end) continue
+}
+
+// Run so slow
+function longRunningFn(args) {
+    sleep(3000)
+    return `longRunningFn result ${args}`
+}
+
+const memoize = (f) => {
+    const cache = {};
+
+    return (...args) => {
+        const argStr = JSON.stringify(args);
+        cache[argStr] = cache[argStr] || f(...args);
+        return cache[argStr]; Å
+    };
+};
+
+const memoizedlongRunningFn = memoize(longRunningFn);
+
+console.log(memoizedlongRunningFn("abc"))
+console.log(memoizedlongRunningFn("abc"))
+
+// console.log(longRunningFn("abc"))
+// console.log(longRunningFn("abc"))
\ No newline at end of file
diff --git a/functional-programming.js/first-class-function.js b/functional-programming.js/first-class-function.js
new file mode 100644
index 0000000..3d132cc
--- /dev/null
+++ b/functional-programming.js/first-class-function.js
@@ -0,0 +1,50 @@
+const firstClassFn = function (str) {
+    console.log(str);
+}
+
+firstClassFn("Ha Vi");
+console.log(typeof firstClassFn)
+console.log(firstClassFn instanceof Object)
+
+// Use synchronous callback
+const useCallBackFn = function (callBackFn) {
+    callBackFn();
+}
+
+useCallBackFn(function () {
+    console.log("Ha vi in callback")
+})
+
+// Use asynchronous callback
+const useAsyncFn = function (asyncFn) {
+    console.log("Ha vi call immediately")
+    setTimeout(asyncFn, 2000)
+}
+
+useAsyncFn(function () {
+    console.log("Ha vi call after 2s")
+})
+
+// 
+const isTrue = function (value, callback) {
+    if (value === true) {
+        callback(null, "Value was true.");
+    }
+    else {
+        callback(new Error("Value is not true!"));
+    }
+}
+
+const callback = function (error, retval) {
+    if (error) {
+        console.log(error);
+        return;
+    }
+    console.log(retval);
+}
+
+// Note: when calling the same asynchronous function twice like this, you are in a race condition.
+// You have no way of knowing for certain which callback will be called first when calling the functions in this manner.
+
+isTrue(false, callback);
+isTrue(true, callback);
\ No newline at end of file
diff --git a/functional-programming.js/pure-function.js b/functional-programming.js/pure-function.js
new file mode 100644
index 0000000..5ef380a
--- /dev/null
+++ b/functional-programming.js/pure-function.js
@@ -0,0 +1,16 @@
+const pureFn = (arr) => {return arr[0]};
+const arr = [2,3,4];
+console.log(pureFn(arr));
+
+const impureFn = function(arr) {
+    arr.forEach((element, index) => {
+        arr[index] = element + 1;
+    })
+
+    return arr;
+}
+
+console.log(arr);
+console.log(impureFn(arr));
+console.log(arr);
+
diff --git a/trie-go/trie.go b/trie-go/trie.go
new file mode 100644
index 0000000..ba30701
--- /dev/null
+++ b/trie-go/trie.go
@@ -0,0 +1,71 @@
+package main
+
+import "fmt"
+
+const (
+	//ALBHABET_SIZE total characters in english alphabet
+	ALBHABET_SIZE = 26
+)
+
+type trieNode struct {
+	childrens [ALBHABET_SIZE]*trieNode
+	isWordEnd bool
+}
+
+type trie struct {
+	root *trieNode
+}
+
+func initTrie() *trie {
+	return &trie{
+		root: &trieNode{},
+	}
+}
+
+func (t *trie) insert(word string) {
+	wordLength := len(word)
+	current := t.root
+	for i := 0; i < wordLength; i++ {
+		index := word[i] - 'a'
+		if current.childrens[index] == nil {
+			current.childrens[index] = &trieNode{}
+		}
+		current = current.childrens[index]
+	}
+	current.isWordEnd = true
+}
+
+func (t *trie) find(word string) bool {
+	wordLength := len(word)
+	current := t.root
+	for i := 0; i < wordLength; i++ {
+		index := word[i] - 'a'
+		if current.childrens[index] == nil {
+			return false
+		}
+		current = current.childrens[index]
+	}
+	if current.isWordEnd {
+		return true
+	}
+	return false
+}
+
+func main() {
+	trie := initTrie()
+	words := []string{"sam", "john", "tim", "jose", "rose",
+		"cat", "dog", "dogg", "roses"}
+	for i := 0; i < len(words); i++ {
+		trie.insert(words[i])
+	}
+	wordsToFind := []string{"sam", "john", "tim", "jose", "rose",
+		"cat", "dog", "dogg", "roses", "rosess", "ans", "san"}
+	for i := 0; i < len(wordsToFind); i++ {
+		found := trie.find(wordsToFind[i])
+		if found {
+			fmt.Printf("Word \"%s\" found in trie\n", wordsToFind[i])
+		} else {
+			fmt.Printf("Word \"%s\" not found in trie\n", wordsToFind[i])
+		}
+	}
+}