Javascript parseInt()

Introduction

The Javascript parseInt() function parses a string to an integer.

We can specify radix, which is the base in mathematical numeral systems. 

parseInt(string [, radix])
Parameters Optional Meaning
stringNotThe value to parse.
radixOptional An integer between 2 and 36 that represents the radix

parseInt() return NaN when

  • the radix is smaller than 2 or bigger than 36
  • the first non-whitespace character cannot be converted to a number.

parseInt() understands two signs: + for positive, and - for negative.

parseInt() converts a BigInt to a Number and loses precision.

Using parseInt(). 

console.log(parseInt('0xF', 16));
console.log(parseInt('F', 16));
console.log(parseInt('17', 8));
console.log(parseInt(021, 8));/*from   w w  w.  j a va  2 s  .c  om*/
console.log(parseInt('015', 10)    );
console.log(parseInt(015, 10)    );
console.log(parseInt(15.99, 10));

Using parseInt(). 

console.log(parseInt('15,123', 10));
console.log(parseInt('F123', 16));
console.log(parseInt('1111', 2));
console.log(parseInt('15*3', 10));
console.log(parseInt('15e2', 10));
console.log(parseInt('15px', 10));
console.log(parseInt('12', 13));

Using parseInt(). 

console.log(parseInt('-F', 16));
console.log(parseInt('-0F', 16));
console.log(parseInt('-0XF', 16));
console.log(parseInt(-15.1, 10));
console.log(parseInt('-17', 8));
console.log(parseInt('-15', 10));
console.log(parseInt('-1111', 2));
console.log(parseInt('-15e1', 10));
console.log(parseInt('-12', 13));

The following examples all return NaN: 

console.log(parseInt('Hello', 8));
console.log(parseInt('546', 2));    // Digits other than 0 or 1 are invalid for binary radix

BigInt values lose precision: 

console.log(parseInt('900719925474099267n'));



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