Create 02_Create a Stack Class.md

Author: ps0305

Coding Interview Prep/Data Structures/02_Create a Stack Class.md

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+Although you can use arrays to create stacks, sometimes it is best to limit the amount of control we have with our stacks.
+Apart from the push and pop method, stacks have other useful methods.
+Let's add a `peek`, `isEmpty`, and `clear` method to our stack class.
+
+Write a `push` method that pushes an element to the top of the stack,
+a `pop` method that removes the element on the top of the stack,
+a `peek` method that looks at the first element in the stack, an `isEmpty` method that checks if the stack is empty,
+and a `clear` method that removes all elements from the stack.
+Normally stacks don't have this, but we've added a print helper method that console logs the collection.
+
+
+```js
+function Stack() {
+  var collection = [];
+  this.print = function() {
+    console.log(collection);
+  };
+  // Only change code below this line
+  this.push = function(el) {
+    collection.push(el);
+  }
+
+  this.pop = function() {
+    return collection.pop()
+  }
+
+  this.peek = function() {
+    return collection[collection.length - 1]
+  }
+
+  this.isEmpty = function() {
+    return (collection.length === 0);
+  }
+
+  this.clear = function() {
+    collection = [];
+  }
+  // Only change code above this line
+}
+