JavaScript - parseInt() method

revision:

Category : number

The Number.parseInt() static method parses a string argument and returns an integer of the specified radix or base.

Syntax : 

        Number.parseInt(string)
        Number.parseInt(string, radix)

Parameters:

string : required. The value to parse, coerced to a string. Leading whitespace in this argument is ignored.

radix : optional. An integer between 2 and 36 that represents the radix (the base in mathematical numeral systems) of the string. If radix is undefined or 0, it is assumed to be 10 except when the number begins with the code unit pairs 0x or 0X, in which case a radix of 16 is assumed.

Examples:

        function roughScale(x, base) {
            const parsed = Number.parseInt(x, base);
            if (Number.isNaN(parsed)) {
              return 0;
            }
            return parsed * 100;
        }
        console.log(roughScale(' 0xF', 16));
          // Expected output: 1500
        console.log(roughScale('321', 2));
          // Expected output: 0

Practical examples

example: parse a string and return the first integer.

code: 
                    <div>
                        <p id="parse-1"></p>
                    </div>
                    <script>
                        document.getElementById("parse-1").innerHTML = "parse a string and return the first integer : " + "<br>" +
                            Number.parseInt("10") + "<br>" +
                            Number.parseInt("10.00") + "<br>" +
                            Number.parseInt("10.33") + "<br>" +
                            Number.parseInt("34 45 66") + "<br>" +
                            Number.parseInt("   60   ") + "<br>" +
                            Number.parseInt("40 years") + "<br>" +
                            Number.parseInt("He was 40");
                    </script>

example: parse a string and return the first integer.

code: 
                    <div>
                        <p id="parse-2"></p>
                    </div>
                    <script>
                        document.getElementById("parse-2").innerHTML = "parse a string and return the first integer : " + "<br>" +
                            Number.parseInt("10", 10) + "<br>" +
                            Number.parseInt("010") + "<br>" +
                            Number.parseInt("10", 8) + "<br>" +
                            Number.parseInt("0x10 ") + "<br>" +
                            Number.parseInt("10", 16) + "<br>" 
                        
                    </script>