<pre class="shiki github-dark shaku"><code>/* Array is disabled in your code */// you need to complete the following Classclass Queue { queue = []; enqueue(element) { // add new element to the rare this.queue[this.queue.length] = element; return this.queue; } peek() { // get the head element if(this.queue.length &gt;= 0) return this.queue[0]; else return undefined; } size() { // return count of element return this.queue.length; } dequeue() { // remove the head element return this.queue.shift(); }}const queue = new Queue();console.log(queue.enqueue(1))console.log(queue.enqueue(2))console.log(queue.peek())console.log(queue.size())console.log(queue.dequeue(1))</code></pre>

space complexity of O(n)  and time complexity of O(1) for peek and size and O(n) for enqueue and dequeue

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In JavaScript, we could use array to work as both a Stack or a queue. const arr = [1, 2, 3, 4]arr.push(5) // now array is [1, 2, 3, 4, 5]arr.pop() // …