<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title></title> </head> <body> <script type="text/javascript"> let log = console.log.bind(console); let x = [1, 2, 3]; x.isEmpty = function() { if (this.length == 0) { return true; } else { return false; } }; x.push(4); log("isEmpty", x.isEmpty()); // => isEmpty false log(x); // => [1, 2, 3, 4] log(x.pop()); // => 4 log(x.pop()); // => 3 log(x.pop()); // => 2 log(x.pop()); // => 1 log(x.pop(), "??"); // => undefined ?? log("isEmpty", x.isEmpty()); // => isEmpty true </script> <script type="text/javascript"> // 利用数组Q[0..n]（有效下标是0~n-1）实现一个最多容纳n-1个元素的队列 let queue = []; queue.size = 12; queue.tail = queue.head = 0; function enqueue(q, x) { let temp = (q.tail == q.size - 1) ? 0 : q.tail + 1; if (temp == q.head) { // 有效下标是12个的数组，只能存11个数 throw new Error("overflow"); } else { q[q.tail] = x; q.tail = temp; } } function dequeue(q) { if (q.head == q.tail) { throw new Error("underflow"); } else { let x = q[q.head]; if (q.head == q.size - 1) { q.head = 1; } else { ++q.head; } return x; } } log(queue); for (let i = 0; i != queue.size - 1; ++i) { enqueue(queue, i); } log(queue); // => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, size: 12, head: 0, tail: 11] for (let i = 0; i != queue.size - 1; ++i) { log(dequeue(queue)); } dequeue(queue); // => Uncaught Error: underflow </script> </body> </html>
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