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Discussion on: Key JavaScript Concepts I Mastered During LeetCode’s 30-Day Challenge

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Jon Randy 🎖️ • • Edited

You need be careful with the length property of a function. It actually returns the number of parameters (not arguments - those are what we pass in) a function accepts, but only the number up to the first parameter that doesn't have a default value assigned:

console.log( (a => a).length )  // 1
console.log( ((a, b) => a).length )  // 2
console.log( ((a, b, c=0) => a).length )  // 2
console.log( ((a, b, c=0, d) => a).length ) // 2
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Imran Latif •

Yes, you are correct. In my case, all I needed was a way to get number of parameters a function is accepting to solve a specific LeetCode problem. But yes, one should be careful while using length property on functions due to the reasons you've explained with examples.

Thanks!