javascript string is number code example

Example 1: intval js

parseInt(value);

let string = "321"
console.log(string); // "321" <= string

let number = parseInt(string);
console.log(number) // 321 <=int

Example 2: 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 3: js is number

Number.isInteger(value)

Example 4: javascript is variable a string

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

Example 5: 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 6: js string have number js

var hasNumber = /\d/;   
      hasNumber.test("ABC33SDF");  //true
      hasNumber.test("ABCSDF");  //false