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Merged
merged 3 commits into from
Aug 20, 2020
Merged

new stack implementation (ES6) fixes: #{246} #247

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c7b59a7
new stack implementation (ES6) fixes: #{246}
Makso83 Aug 7, 2020
df5de96
Update Data-Structures/Stack/StackES6.js
itsvinayak Aug 20, 2020
db1f0d6
Update StackES6.js
itsvinayak Aug 20, 2020
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68 changes: 68 additions & 0 deletions Data-Structures/Stack/StackES6.js
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Original file line number Diff line number Diff line change
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/* Stack data-structure. It's work is based on the LIFO method (last-IN-first-OUT).
* It means that elements added to the stack are placed on the top and only the
* last element (from the top) can be reached. After we get access to the last
* element, he pops from the stack.
* This is a class-based implementation of a Stack. It provides functions
* 'push' - to add an element, 'pop' - to remove an element from the top.
* Also it implements 'length', 'last' and 'isEmpty' properties and
* static isStack method to check is an object the instance of Stack class.
*/

// Class declaration
class Stack {
constructor () {
this.stack = []
this.top = 0
}

// Adds a value to the end of the Stack
push (newValue) {
this.stack.push(newValue)
this.top += 1
}

// Returns and removes the last element of the Stack
pop () {
if (this.top !== 0) {
this.top -= 1
return this.stack.pop()
}
throw new Error('Stack Underflow')
}

// Returns the number of elements in the Stack
get length () {
return this.top
}

// Returns true if stack is empty, false otherwise
get isEmpty () {
return this.top === 0
}

// Returns the last element without removing it
get last () {
if (this.top !== 0) {
return this.stack[this.stack.length - 1]
}
return null
}

// Checks if an object is the instance os the Stack class
static isStack (el) {
return el instanceof Stack
}
}
const newStack = new Stack()
console.log('Is it a Stack?,', Stack.isStack(newStack))
console.log('Is stack empty? ', newStack.isEmpty)
newStack.push('Hello world')
newStack.push(42)
newStack.push({ a: 6, b: 7 })
console.log('The length of stack is ', newStack.length)
console.log('Is stack empty? ', newStack.isEmpty)
console.log('Give me the last one ', newStack.last)
console.log('Pop the latest ', newStack.pop())
console.log('Pop the latest ', newStack.pop())
console.log('Pop the latest ', newStack.pop())
console.log('Is stack empty? ', newStack.isEmpty)