4.4 KiB
4.4 KiB
id | title | challengeType |
---|---|---|
587d8250367417b2b2512c5f | Create a Stack Class | 1 |
Description
push
and pop
method, stacks have other useful methods. Let's add a peek
, isEmpty
, and clear
method to our stack class.
Instructions
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.
Instructions
Tests
tests:
- text: Your <code>Stack</code> class should have a <code>push</code> method.
testString: assert((function(){var test = new Stack(); return (typeof test.push === 'function')}()), 'Your <code>Stack</code> class should have a <code>push</code> method.');
- text: Your <code>Stack</code> class should have a <code>pop</code> method.
testString: assert((function(){var test = new Stack(); return (typeof test.pop === 'function')}()), 'Your <code>Stack</code> class should have a <code>pop</code> method.');
- text: Your <code>Stack</code> class should have a <code>peek</code> method.
testString: assert((function(){var test = new Stack(); return (typeof test.peek === 'function')}()), 'Your <code>Stack</code> class should have a <code>peek</code> method.');
- text: Your <code>Stack</code> class should have a <code>isEmpty</code> method.
testString: assert((function(){var test = new Stack(); return (typeof test.isEmpty === 'function')}()), 'Your <code>Stack</code> class should have a <code>isEmpty</code> method.');
- text: Your <code>Stack</code> class should have a <code>clear</code> method.
testString: assert((function(){var test = new Stack(); return (typeof test.clear === 'function')}()), 'Your <code>Stack</code> class should have a <code>clear</code> method.');
- text: The <code>peek</code> method should return the top element of the stack
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');
- text: The <code>pop</code> method should remove and return the top element of the stack
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');
- text: The <code>isEmpty</code> method should return true if a stack does not contain any elements
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');
- text: The <code>clear</code> method should remove all element from the stack
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');
Challenge Seed
function Stack() {
var collection = [];
this.print = function() {
console.log(collection);
};
// Only change code below this line
// Only change code above this line
}
Solution
class Stack {
constructor() {
this.collection = [];
}
print(){
console.log(this.collection);
}
push(val){
this.collection.push(val);
}
pop(){
return this.collection.pop();
}
peek(){
return this.collection[this.collection.length-1];
}
isEmpty(){
return this.collection.length === 0;
}
clear(){
return this.collection.length = 0;
}
}