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Today I solved my first LeetCode problem. Small milestone, but an important one for me. (1/5)

The task was to add a last() method to Array.prototype. My immediate intuition was to use this, because the method is reused and invoked at the call site. Runtime-bound, call-site-dependent behavior fits perfectly here. (2/5)

6/1/26, 3:45 pm0 reposts0 likes

Niraj Bajaj

@nirajbajaj.dev

6 Jan

That intuition didn’t come from nowhere. It came directly from reading You Don’t Know JS Yet: this & Object Prototypes by Kyle Simpson. (3/5)

Niraj Bajaj

@nirajbajaj.dev

6 Jan

Here was my solution: Array.prototype.last = function () { if (this.length === 0) return -1; return this[this.length - 1]; }; (4/5) #JavaScript #DSA #LeetCode

Niraj Bajaj

@nirajbajaj.dev

6 Jan

What made this special wasn’t the code, but realizing I reached for this instinctively and correctly. That’s what good teaching does. Thank you Kyle Simpson. (5/5)