10 ways to Convert String to a Number in JavaScript

1. Using parseInt() function:

The parseInt() function parses a string argument and returns an integer.




Example 1: String to int

console.log(parseInt('100'));

100





Example 2: String to int with base 2

console.log(parseInt('200', 2));

200




Example 3: White-spaces are ignored.

console.log(parseInt('   300   '));

300




Example 4: Leading zero's are ignored.

console.log(parseInt('000400'));

400




Example 5: Decimal's are ignored.

console.log(parseInt('500.678'));

500

Note: The decimals are ignored when using parseInt() function to convert String to Int.

If the String value provided is not a valid number, then we get NaN as an output.




Example 6: NaN output for Invalid String Number.

console.log(parseInt('hello'));

NaN




Summary: parseInt()

• It accepts an optional second argument (radix) that specifies the base of the number.
• Leading whitespace is ignored.
• Leading zeros are ignored.
• Decimals are ignored..
• If the string starts with '0x' or '0X', it's interpreted as a hexadecimal number.
• If the string doesn't start with a valid numeric character, parseInt() returns NaN.
• If the radix is not specified or is 0, JavaScript assumes base 10.
• If the radix is not in the range 2-36 or is not a number, parseInt() returns NaN.
• Negative numbers can be parsed by including a '-' sign at the beginning.
• If the string contains non-numeric characters after valid numeric characters, parseInt() stops parsing at the non-numeric character.
• If the string is empty or contains only non-numeric characters, parseInt() returns NaN

2. Using parseFloat() function

The parseFloat() function parses a string argument and returns a floating point number.




Example 7:

console.log(parseFloat('600'));

600





Example 8:

console.log(parseFloat('700.89'));

700.89




Example 9:

console.log(parseFloat('   800.1   '));

800.1




Example 10:

console.log(parseFloat('000900.1'));

900.1




Example 11:

console.log(parseFloat('Code2care'));

NaN

3. Using Number() Constructor

Example 12:

console.log(Number('1200'));

1200

4. Using + Operator

Example 13:

console.log(+'1300');

1300

5. Math.floor() function (truncates decimal)

Example 14:

console.log(Math.floor('1400.2'));

1400

6. Math.round() function (rounds up/down decimals)

Example 15:

console.log(Math.round('1500.7'));
console.log(Math.round('1500.2'));

1501
1500

7. Math.ceil() function (rounds up decimals)

Example 16:

console.log(Math.ceil('1600.2'));

1600

8. BigInt() Constructor

Example 17:

console.log(String(BigInt('238923820340230470237')));

238923820340230470237

9. Bitwise OR | Operator

Example 18:

console.log("1800" | 0);

1800

10. Implicit Type Conversion

Example 19:

When we do arithmetic operation with a String and a Number, JavaScript automatically converts strings into a number.

console.log("19"*100);

1900

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