Interview Q&A / JavaScript
JavaScript interview questions
Closures, the event loop, this, promises and the core language questions every frontend round asks.
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- Why does ['1', '2', '3'].map(parseInt) not give [1, 2, 3]?
map passes three arguments to the callback: item, index and array. parseInt uses the second as the radix, so it runs parseInt('2', 1) and parseInt('3', 2), both NaN. Use map(Number) or map(s => parseInt(s, 10)).
IntermediateQuick answer1 min read