js validate string is 4 charts of numbers code example

Example 1: javascript is variable a string

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

Example 2: 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

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