102 lines
4.4 KiB
Markdown
102 lines
4.4 KiB
Markdown
---
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id: 587d8250367417b2b2512c5f
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title: Create a Stack Class
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challengeType: 1
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---
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## Description
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<section id='description'>
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In the last section, we talked about what a stack is and how we can use an array to represent a stack. In this section, we will be creating our own stack class.
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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.
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Apart from the <code>push</code> and <code>pop</code> method, stacks have other useful methods. Let's add a <code>peek</code>, <code>isEmpty</code>, and <code>clear</code> method to our stack class.
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Instructions
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Write a <code>push</code> method that pushes an element to the top of the stack, a <code>pop</code> method that removes the element on the top of the stack, a <code>peek</code> method that looks at the first element in the stack, an <code>isEmpty</code> method that checks if the stack is empty, and a <code>clear</code> method that removes all elements from the stack.
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Normally stacks don't have this, but we've added a <code>print</code> helper method that console logs the collection.
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</section>
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## Instructions
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<section id='instructions'>
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: Your <code>Stack</code> class should have a <code>push</code> method.
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testString: assert((function(){var test = new Stack(); return (typeof test.push === 'function')}()), 'Your <code>Stack</code> class should have a <code>push</code> method.');
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- text: Your <code>Stack</code> class should have a <code>pop</code> method.
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testString: assert((function(){var test = new Stack(); return (typeof test.pop === 'function')}()), 'Your <code>Stack</code> class should have a <code>pop</code> method.');
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- text: Your <code>Stack</code> class should have a <code>peek</code> method.
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testString: assert((function(){var test = new Stack(); return (typeof test.peek === 'function')}()), 'Your <code>Stack</code> class should have a <code>peek</code> method.');
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- text: Your <code>Stack</code> class should have a <code>isEmpty</code> method.
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testString: assert((function(){var test = new Stack(); return (typeof test.isEmpty === 'function')}()), 'Your <code>Stack</code> class should have a <code>isEmpty</code> method.');
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- text: Your <code>Stack</code> class should have a <code>clear</code> method.
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testString: assert((function(){var test = new Stack(); return (typeof test.clear === 'function')}()), 'Your <code>Stack</code> class should have a <code>clear</code> method.');
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- text: The <code>peek</code> method should return the top element of the stack
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testString: assert((function(){var test = new Stack(); test.push('CS50'); return (test.peek() === 'CS50')}()), 'The <code>peek</code> method should return the top element of the stack');
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- text: The <code>pop</code> method should remove and return the top element of the stack
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testString: assert((function(){var test = new Stack(); test.push('CS50'); return (test.pop() === 'CS50');}()), 'The <code>pop</code> method should remove and return the top element of the stack');
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- text: The <code>isEmpty</code> method should return true if a stack does not contain any elements
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testString: assert((function(){var test = new Stack(); return test.isEmpty()}()), 'The <code>isEmpty</code> method should return true if a stack does not contain any elements');
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- text: The <code>clear</code> method should remove all element from the stack
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testString: assert((function(){var test = new Stack(); test.push('CS50'); test.clear(); return (test.isEmpty())}()), 'The <code>clear</code> method should remove all element from the stack');
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function Stack() {
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var collection = [];
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this.print = function() {
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console.log(collection);
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};
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// Only change code below this line
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// Only change code above this line
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}
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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class Stack {
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constructor() {
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this.collection = [];
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}
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print(){
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console.log(this.collection);
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}
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push(val){
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this.collection.push(val);
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}
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pop(){
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return this.collection.pop();
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}
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peek(){
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return this.collection[this.collection.length-1];
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}
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isEmpty(){
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return this.collection.length === 0;
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}
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clear(){
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return this.collection.length = 0;
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}
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}
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```
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</section>
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