js check if string or number code example

Example 1: javascript check if string is number

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

// can be wrapped for making simple and readable
function isNumeric(num){
  return !isNaN(num)
}

isNumeric(123)         // true
isNumeric('123')       // true
isNumeric('1e10000')   // true (This translates to Infinity, which is a number)
isNumeric('foo')       // false
isNumeric('10px')      // false

Example 2: javascript is variable a string

if (typeof myVar === 'string'){
    //I am indeed a string
}

Example 3: js check if string is number

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

isNaN(123)         // false
isNaN('123')       // false
isNaN('1e10000')   // false (This translates to Infinity, which is a number)
isNaN('foo')       // true
isNaN('10px')      // true

Example 4: To check if a value is a number in JavaScript

const value = 2
isNaN(value) //false
isNaN('test') //true
isNaN({}) //true
isNaN(1.2) //false

Example 5: js check if string or int

var myString     =  "abc123";
var otherString  =  "123";
/* isInterger() checks if an value repersents an int  */

Number.isInteger(myString);    //returns false
Number.isInteger(otherString); //returns true