The $4.35 Item That Was Charged $4.34
Why 0.1 + 0.2 !== 0.3 in JavaScript, how floating-point math drops a cent when converting dollars to cents, and why money should be stored as integers.
5 min read
Why 0.1 + 0.2 !== 0.3 in JavaScript, how floating-point math drops a cent when converting dollars to cents, and why money should be stored as integers.
Why JavaScript object key order puts integer-like keys first in ascending order, how that silently reorders JSON from your API, and when to use an array or Map.
How automatic semicolon insertion (ASI) turns `return` followed by a newline into `return;`, and the lines where JavaScript refuses to add a semicolon at all.
Why ['1', '7', '11'].map(parseInt) returns [1, NaN, 3]: map passes the index as parseInt's radix. Plus the Number('') trap hiding in the obvious fix.
Why JavaScript's sort() compares numbers as strings, why a 'lazy' comparator works in Safari but breaks in Chrome, and the one-line fix.