add stack js implementation

Author: imteekay

computer_science/data_structures/stack/stack.js

@@ -0,0 +1,40 @@
+const push = (stack, item) => [item, ...stack];
+
+const pop = (stack) => stack.slice(1);
+
+const top = (stack) => stack[0];
+
+const isEmpty = (stack) => size(stack) === 0;
+
+const size = (stack) => stack.length;
+
+// testing
+let stack = [];
+
+console.log(isEmpty(stack));
+
+stack = push(stack, 1);
+console.log(stack);
+stack = push(stack, 2);
+console.log(stack);
+stack = push(stack, 3);
+console.log(stack);
+stack = push(stack, 4);
+console.log(stack);
+stack = push(stack, 5);
+console.log(stack);
+
+console.log(top(stack));
+console.log(size(stack));
+console.log(isEmpty(stack));
+
+stack = pop(stack);
+stack = pop(stack);
+stack = pop(stack);
+stack = pop(stack);
+
+console.log(isEmpty(stack));
+console.log(top(stack));
+stack = pop(stack);
+console.log(isEmpty(stack));
+console.log(size(stack));

computer_science/data_structures/stack/stack_class.js

@@ -0,0 +1,61 @@
+class Stack {
+  constructor() {
+    this.items = [];
+  }
+
+  push(item) {
+    this.items = [item, ...this.items];
+  }
+
+  pop() {
+    this.items = this.items.slice(1);
+  }
+
+  top() {
+    return this.items[0];
+  }
+
+  isEmpty() {
+    return this.size() === 0;
+  }
+
+  size() {
+    return this.items.length;
+  }
+}
+
+// testing
+const stack = new Stack();
+
+console.log(stack.isEmpty());
+
+stack.push(1);
+console.log(stack.items);
+stack.push(2);
+console.log(stack.items);
+stack.push(3);
+console.log(stack.items);
+stack.push(4);
+console.log(stack.items);
+stack.push(5);
+console.log(stack.items);
+
+console.log(stack.isEmpty());
+console.log(stack.top());
+
+stack.pop();
+console.log(stack.items);
+stack.pop();
+console.log(stack.items);
+stack.pop();
+console.log(stack.items);
+stack.pop();
+console.log(stack.items);
+
+console.log(stack.isEmpty());
+
+stack.pop();
+console.log(stack.items);
+
+console.log(stack.isEmpty());
+console.log(stack.top());

computer_science/data_structures/stack/stack_closure.js

@@ -0,0 +1,55 @@
+const createStack = () => {
+  let items = [];
+
+  const push = (item) => items = [item, ...items];
+  const pop = () => items = items.slice(1);
+  const top = () => items[0];
+  const isEmpty = () => size() === 0;
+  const size = () => items.length;
+  const getItems = () => items;
+
+  return {
+    push,
+    pop,
+    top,
+    isEmpty,
+    size,
+    getItems
+  };
+};
+
+// testing
+const stack = createStack();
+
+console.log(stack.isEmpty());
+
+stack.push(1);
+console.log(stack.getItems());
+stack.push(2);
+console.log(stack.getItems());
+stack.push(3);
+console.log(stack.getItems());
+stack.push(4);
+console.log(stack.getItems());
+stack.push(5);
+console.log(stack.getItems());
+
+console.log(stack.top());
+console.log(stack.size());
+console.log(stack.isEmpty());
+
+stack.pop();
+console.log(stack.getItems());
+stack.pop();
+console.log(stack.getItems());
+stack.pop();
+console.log(stack.getItems());
+stack.pop();
+console.log(stack.getItems());
+
+console.log(stack.isEmpty());
+console.log(stack.top());
+stack.pop();
+console.log(stack.getItems());
+console.log(stack.isEmpty());
+console.log(stack.size());