is string integer javascript code example

Example 1: Javascript string to int

var myInt = parseInt("10.256"); //10
var myFloat = parseFloat("10.256"); //10.256

Example 2: javascript check if number

function isNumber(n) { return /^-?[\d.]+(?:e-?\d+)?$/.test(n); } 

------------------------

isNumber('123'); // true  
isNumber('123abc'); // false  
isNumber(5); // true  
isNumber('q345'); // false
isNumber(null); // false
isNumber(undefined); // false
isNumber(false); // false
isNumber('   '); // false

Example 3: js check if string is integer

function isInt(str) {
  return !isNaN(str) && Number.isInteger(parseFloat(str));
}

Example 4: javascript pareseint

parseInt(string, radix);

console.log(parseInt(' 0xF', 16));
// expected output: 1500

console.log(parseInt('321', 2));
// expected output: 0

console.log(parseInt('321', 10));
// expected output: 321

/* 
 * @param string Required. The value to parse. If this argument is not
 * a string, then it is converted to one using the ToString abstract
 * operation. Leading whitespace in this argument is ignored.
 *
 * radix
 * @param radix Optional. An integer between 2 and 36 that represents
 * the radix (the base in mathematical numeral systems) of the string.
 * Be careful—this does not default to 10!
 * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt#Description
 * for what happens when radix is not provided
 */

Example 5: how to check if a string is an integer javascript

isNaN(num)         // returns true if the variable does NOT contain a valid number