JavaScript & TypeScript

Types, asynchronous code, modules and JavaScript runtime edge cases.

100 troubleshooting guides · Page 2 / 5

25. How do I send a BigInt sequence through JSON without losing digits?

    Define that field as a decimal string in the transport contract and send sequence.toString().

26. Why does comparing two input values put 9 after 10?

    Input values are strings, and two strings compare lexicographically.

27. Why does a fallback overwrite a saved zero-percent discount?

    Logical OR replaces every falsy value, including zero.

28. Why does optional callback invocation throw for JSON configuration?

    config.onSave?.() only skips nullish values; a present string is not callable.

29. Why does a destructured API limit stay null despite a default?

    Destructuring defaults apply only to undefined.

30. Why does editing a copied settings draft alter the live nested settings?

    Spread copies one level, leaving nested references shared.

31. Why does cloning a configuration object unexpectedly call its getters?

    Object.assign and spread read enumerable property values.

32. Why do numbered object keys reorder imported workflow steps?

    Array-index-like keys have special enumeration ordering.

33. Why does hasOwnProperty crash on a null-prototype dictionary?

    The dictionary does not inherit Object.prototype methods.

34. Why does a composite object key miss an existing Map cache entry?

    A newly constructed key object has a different identity.

35. Why does a service method lose this when registered as an event listener?

    The event system invokes the detached function with its own receiver.

36. Why does an arrow method ignore call and bind when changing this?

    An arrow captures lexical this when created.

37. Why does a private-field class method fail when passed to a timer?

    Private fields require the correct class instance as receiver.

38. Why do delayed callbacks in a var loop all process the final row?

    They share one function-scoped variable.

39. Why does typeof throw inside a block before a let declaration?

    The lexical binding is in its temporal dead zone until initialized.

40. Why does reassignment of an imported configuration flag fail?

    ES imports are live, read-only bindings from the importer’s perspective.

41. Why is the result of dynamic import not callable?

    Dynamic import resolves to a module namespace.

42. Why does a Base64 query token lose its plus signs?

    Parsing form-style query text treats plus as space.

43. Why does a date-only API field display yesterday in an American time zone?

    The standard YYYY-MM-DD form parses as UTC; local formatting can move it to the previous calendar day.

44. Why does adding 24 hours move a local appointment time across daylight saving?

    An elapsed 24 hours and the next local calendar day are different operations.

45. Why does an invalid API date crash only when serialized?

    An Invalid Date can exist until toISOString throws.

46. How do I sort Turkish names with dotted and dotless I consistently?

    Use new Intl.Collator("tr", {sensitivity:"base"}).compare for Turkish user-facing sorting.

47. How do I truncate a notification without breaking joined emoji?

    Segment text with Intl.Segmenter using grapheme granularity and keep complete segments.

48. Why does a visible ten-character name fail a JavaScript length limit?

    String.length counts UTF-16 code units, not visible characters.

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