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parseInt() - JavaScript | MDN
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parseInt()

Baseline Widely available

This feature is well established and works across many devices and browser versions. Its been available across browsers since 2015 ..

parseInt() .

In this article

console.log(parseInt("123"));
// 123 (default base-10)
console.log(parseInt("123", 10));
// 123 (explicitly specify base-10)
console.log(parseInt("   123 "));
// 123 (whitespace is ignored)
console.log(parseInt("077"));
// 77 (leading zeros are ignored)
console.log(parseInt("1.9"));
// 1 (decimal part is truncated)
console.log(parseInt("ff", 16));
// 255 (lower-case hexadecimal)
console.log(parseInt("0xFF", 16));
// 255 (upper-case hexadecimal with "0x" prefix)
console.log(parseInt("xyz"));
// NaN (input can't be converted to an integer)


parseInt(string, radix);

string

, . string , ( ToString). .

radix

2 36, string, . 10. , . , .

, ( ) . , NaN.

parseInt , NaN. ( NaN) (string), (radix). , 10 , 8 - , 16 - . 10, 9 . , ( 16) A F.

parseInt , , (, ) , , . parseInt . .

e (, 6.022e23), parseInt , . parseInt Math.floor().

undefined ( ) 0 ( ), JavaScript :

  • string "0x" "0X", 16, .
  • string "0", 8, 10, . ECMAScript 5 10 ( ), , parseInt.
  • string , ( 10).

, parseInt NaN.

, NaN - . , parseInt NaN , isNaN. NaN , NaN.

, intValue.toString(radix).

: parseInt

15:

js
parseInt(" 0xF", 16);
parseInt(" F", 16);
parseInt("17", 8);
parseInt(021, 8);
parseInt("015", 10); //parseInt(015, 10);  15
parseInt(15.99, 10);
parseInt("FXX123", 16);
parseInt("1111", 2);
parseInt("15*3", 10);
parseInt("15e2", 10);
parseInt("15px", 10);
parseInt("12", 13);

NaN:

js
parseInt("Hello", 8); //   
parseInt("546", 2); //

-15:

js
parseInt("-F", 16);
parseInt("-0F", 16);
parseInt("-0XF", 16);
parseInt(-15.1, 10);
parseInt(" -17", 8);
parseInt(" -15", 10);
parseInt("-1111", 2);
parseInt("-15e1", 10);
parseInt("-12", 13);

4:

js
parseInt(4.7, 10);
parseInt(4.7 * 1e22, 10); //     4
parseInt(0.00000000000434, 10); //     4

224:

js
parseInt("0e0", 16);

ECMAScript 3 ECMAScript 5, , 0, . , . , .

js
parseInt("0e0"); // 0
parseInt("08"); // 0, '8'      .

ECMAScript 5

ECMAScript 5 parseInt , 0. ECMAScript 5 :

parseInt . . 0, 10, , 0x 0X: 16. 16, 0x 0X.

ECMAScript 5 ECMAScript 3, , .

2013 , , .

. :

js
var filterInt = function (value) {
  if (/^(\-|\+)?([0-9]+|Infinity)$/.test(value)) return Number(value);
  return NaN;
};

console.log(filterInt("421")); // 421
console.log(filterInt("-421")); // -421
console.log(filterInt("+421")); // 421
console.log(filterInt("Infinity")); // Infinity
console.log(filterInt("421e+0")); // NaN
console.log(filterInt("421hop")); // NaN
console.log(filterInt("hop1.61803398875")); // NaN
console.log(filterInt("1.61803398875")); // NaN

Specification
ECMAScript 2027 LanguageSpecification
# sec-parseint-string-radix

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