Node.js 10‑12 Tricks: Optional Catch, Trim, Symbol Description, Array Flat, JSON Fix

Optional catch binding

Supported in Node 10+

Example of parsing JSON with try/catch, showing that the catch parameter can be omitted.

let parseResult = someString;
try {
  parseResult = JSON.parse(parseResult);
} catch (unused) {
}

With this feature, the catch binding can omit the parameter and parentheses:

let parseResult = someString;
try {
  parseResult = JSON.parse(parseResult);
} catch {
}

String whitespace removal

Supported in Node 10+

Remove leading spaces

const str = "   Node 地下铁!   ";
str.trimStart(); // or str.trimLeft()

Remove trailing spaces

const str = "   Node 地下铁!   ";
str.trimEnd(); // or str.trimRight()

Symbol description string

Supported in Node 11+

Symbol values are unique; toString() returns a string like "Symbol(123)". Direct concatenation throws a TypeError. The new description property returns the description without the wrapper.

Symbol(123).toString(); // "Symbol(123)"
// Symbol(123) + "test" -> TypeError
Symbol(123).description; // "123"
Symbol(123).description + "test"; // "123test"

Array flattening

Supported in Node 11+

The flat method merges nested arrays up to a given depth (default 1).

const arr = ["N", ["o","d"], "e", ["地","下"], "铁"];
arr.flat(); // ["N","o","d","e","地","下","铁"]

const arr2 = ["N", ["o",["d",["e",["地",["下",["铁"]]]]]]];
arr2.flat(6); // ["N","o","d","e","地","下","铁"]

The flatMap method applies a function then flattens one level.

const arr = ["Node","", "地下铁"];
arr.map(s => s.split("")); // [["N","o","d","e"],[],["地","下","铁"]]
arr.flatMap(s => s.split("")); // ["N","o","d","e","地","下","铁"]

More compliant JSON

Supported in Node 12+

JSON.stringify should correctly escape Unicode surrogate pairs.

JSON.stringify('𝌆') === JSON.stringify('\uD834\uDF06'); // true
// Expected escaped form: "\\uD834\\uDF06"

Object.fromEntries

Supported in Node 12+

Converts a list of key‑value pairs into an object.

const obj = Object.fromEntries([
  ["name", "test"],
  ["value", "testValue"]
]);
// { name: "test", value: "testValue" }