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parseFloat()

Baseline

20157

parseFloat() 

function circumference(r) {
  return parseFloat(r) * 2.0 * Math.PI;
}

console.log(circumference(4.567));
// : 28.695307297889173

console.log(circumference("4.567abcdefgh"));
// : 28.695307297889173

console.log(circumference("abcdefgh"));
// : NaN

js
parseFloat(string)

string

ToString

string NaN

: JavaScript parseInt() parseFloat() parseInt("42") parseFloat("42") 42

parseFloat 10 NaN

  • parseFloat (+) (- U+002D HYPHEN-MINUS) (09) (.) (e E)
  • +/- e/E 1 e/E e/E 1 1
  • parseFloat() 0 "Infinity" "-Infinity" Infinity -Infinity
  • parseFloat()
  • parseFloat NaN

parseFloat() Number() parseFloat() 0x0b0o 10 parseFloat() Number() Number() NaN

Number() parseFloat() -1.7976931348623158e+308 1.7976931348623158e+308 Number.MAX_VALUE -Infinity Infinity

parseFloat

3.14

js
parseFloat(3.14);
parseFloat("3.14");
parseFloat("  3.14  ");
parseFloat("314e-2");
parseFloat("0.0314E+2");
parseFloat("3.14some non-digit characters");
parseFloat({
  toString() {
    return "3.14";
  },
});

NaN parseFloat()

NaN

js
parseFloat("FF2");

NaN parseFloat() "NaN" NaN

js
parseFloat("NaN"); // NaN

64 IEEE 754-2019

js
parseFloat("1.7976931348623159e+308"); // Infinity
parseFloat("-1.7976931348623159e+308"); // -Infinity

"Infinity" "-Infinity" Infinity

js
parseFloat("Infinity"); // Infinity
parseFloat("-Infinity"); // -Infinity

parseFloat BigInt

parseFloat() BigInt n BigInt parseFloat()

js
parseFloat(900719925474099267n); // 900719925474099300
parseFloat("900719925474099267n"); // 900719925474099300

n BigInt()

js
BigInt("900719925474099267");
// 900719925474099267n

ECMAScript 2027 LanguageSpecification
# sec-parsefloat-string

MDN

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