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Number Prototype Methods

Number methods format a number as a string; none of them changes the value. To call one on a literal, write (5).toString() or 5..toString(), because 5.toString() reads the dot as a decimal point.

Number prototype methods (valueOf() returns the primitive)
Method Returns (123.456) example
toFixed(digits) fixed decimals (0-100) toFixed(2) → "123.46"
toPrecision(n) n significant digits toPrecision(4) → "123.5"
toExponential(d) scientific notation toExponential(2) → "1.23e+2"
toString(radix) digits in base 2-36 toString(16) → "7b.74bc6a7ef9dc"
toLocaleString(loc, opts) locale-aware text "123.456" (en-US)
Formatting numbers and the toFixed() rounding surpriseJavaScriptLive
console.log((1.005).toFixed(2), (1.005).toPrecision(17), 5..toString(2));
console.log((1234567.891).toLocaleString("de-DE"),
  (2500).toLocaleString("en-GB", { style: "currency", currency: "GBP" }));

(1.005).toFixed(2) gives "1.00", not "1.01", because the double nearest to 1.005 lies just below it. For money, calculate in integer cents (or BigInt) and format with Intl.NumberFormat (NumberFormat). parseInt(str, radix) is the inverse of toString(radix).