<pre class="shiki github-dark shaku"><code>class Queue { constructor() { this.inStack = new Stack(); this.outStack = new Stack(); } enqueue(element) { this.inStack.push(element); } peek() { if (this.outStack.size() === 0) { this.transfer(); } return this.outStack.peek(); } dequeue() { if (this.outStack.size() === 0) { this.transfer(); } return this.outStack.pop(); } size() { return this.inStack.size() + this.outStack.size(); } transfer() { while (this.inStack.size() &gt; 0) { this.outStack.push(this.inStack.pop()); } }}</code></pre>

This is my Solution !

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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() // …