Intuition

Add a last() method to all arrays so that it returns the last element, or -1 if the array is empty.

Approach

Define the method on Array.prototype. If the array is empty, return -1; otherwise, return the last element.

Code

[{"language":"JavaScript","code":"Array.prototype.last = function() {\n  if (this.length === 0) return -1;\n  return this[this.length - 1];\n};","lang":"javascript","html":"<pre class=\"shiki shiki-themes github-light github-dark\" style=\"background-color:#fff;--shiki-dark-bg:#24292e;color:#24292e;--shiki-dark:#e1e4e8\" tabindex=\"0\"><code><span class=\"line\"><span style=\"color:#005CC5;--shiki-dark:#79B8FF\">Array</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">.</span><span style=\"color:#005CC5;--shiki-dark:#79B8FF\">prototype</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">.</span><span style=\"color:#6F42C1;--shiki-dark:#B392F0\">last</span><span style=\"color:#D73A49;--shiki-dark:#F97583\"> =</span><span style=\"color:#D73A49;--shiki-dark:#F97583\"> function</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">() {</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">  if</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> (</span><span style=\"color:#005CC5;--shiki-dark:#79B8FF\">this</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">.</span><span style=\"color:#005CC5;--shiki-dark:#79B8FF\">length</span><span style=\"color:#D73A49;--shiki-dark:#F97583\"> ===</span><span style=\"color:#005CC5;--shiki-dark:#79B8FF\"> 0</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">) </span><span style=\"color:#D73A49;--shiki-dark:#F97583\">return</span><span style=\"color:#D73A49;--shiki-dark:#F97583\"> -</span><span style=\"color:#005CC5;--shiki-dark:#79B8FF\">1</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">;</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">  return</span><span style=\"color:#005CC5;--shiki-dark:#79B8FF\"> this</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">[</span><span style=\"color:#005CC5;--shiki-dark:#79B8FF\">this</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">.</span><span style=\"color:#005CC5;--shiki-dark:#79B8FF\">length</span><span style=\"color:#D73A49;--shiki-dark:#F97583\"> -</span><span style=\"color:#005CC5;--shiki-dark:#79B8FF\"> 1</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">];</span></span>\n<span class=\"line\"><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">};</span></span></code></pre>"}]

Complexity

⏰ Time complexity: O(1)
🧺 Space complexity: O(1)

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