how to check if a string is an integer javascript

1// native returns true if the variable does NOT contain a valid number
2isNaN(num)
3
4// can be wrapped for making simple and readable
5function isNumeric(num){
6  return !isNaN(num)
7}
8
9isNumeric(123)         // true
10isNumeric('123')       // true
11isNumeric('1e10000')   // true (This translates to Infinity, which is a number)
12isNumeric('foo')       // false
13isNumeric('10px')      // false

1if (typeof myVar === 'string'){
2    //I am indeed a string
3}

1function isNumeric(str) {
2
3	// Check if input is string
4	if (typeof str != "string")
5    	return false
6
7	// Use type coercion to parse the _entirety_ of the string
8    // (`parseFloat` alone does not do this).
9	// Also ensure that the strings whitespaces fail
10	return !isNaN(str) && 
11		!isNaN(parseFloat(str)) 
12}

1isNaN(num)         // returns true if the variable does NOT contain a valid number