how to check if a variable is an integer in javascript

how-to-check-if-variable-is-int.js

//
// four different ways to check if a variable is an integer
// from stackoverflow 
// http://stackoverflow.com/questions/14636536/how-to-check-if-a-variable-is-an-integer-in-javascript
//

//Raw solution
function isInt1(value) {
  return !isNaN(value) && parseInt(Number(value)) == value && !isNaN(parseInt(value, 10));
}

// Bitwise

// Simple parse and check
function isInt2(value) {
  var x = parseFloat(value);
  return !isNaN(value) && (x | 0) === x;
}

// Short-circuiting, and saving a parse operation
function isInt3(value) {
  if (isNaN(value)) {
    return false
  }
  var x = parseFloat(value);
  return (x | 0) === x
}

// Both in one shot
function isInt4(value) {
  return !isNaN(value) && (function(x) { return (x | 0) === x; })(parseFloat(value))
}

// Testing:
	
if (isInt1(42)   != true) throw ''; 
if (isInt1("42") != true) throw '';  
if (isInt1(4e2)  != true) throw '';
if (isInt1("4e2")!= true) throw '';
if (isInt1(" 1 ")!= true) throw '';
if (isInt1(""))     throw '';
if (isInt1("  "))   throw '';
if (isInt1(42.1))   throw '';
if (isInt1(null))   throw '';
if (isInt1(NaN))    throw '';
if (isInt1("1  a")) throw '';
if (isInt1("4e2a")) throw '';

if (isInt2(42)   != true) throw ''; 
if (isInt2("42") != true) throw '';  
if (isInt2(4e2)  != true) throw '';
if (isInt2("4e2")!= true) throw '';
if (isInt2(" 1 ")!= true) throw '';
if (isInt2(""))     throw '';
if (isInt2("  "))   throw '';
if (isInt2(42.1))   throw '';
if (isInt2(null))   throw '';
if (isInt2(NaN))    throw '';
if (isInt2("1  a")) throw '';
if (isInt2("4e2a")) throw '';

if (isInt3(42)   != true) throw ''; 
if (isInt3("42") != true) throw '';  
if (isInt3(4e2)  != true) throw '';
if (isInt3("4e2")!= true) throw '';
if (isInt3(" 1 ")!= true) throw '';
if (isInt3(""))     throw '';
if (isInt3("  "))   throw '';
if (isInt3(42.1))   throw '';
if (isInt3(null))   throw '';
if (isInt3(NaN))    throw '';
if (isInt3("1  a")) throw '';
if (isInt3("4e2a")) throw '';

if (isInt4(42)   != true) throw ''; 
if (isInt4("42") != true) throw '';  
if (isInt4(4e2)  != true) throw '';
if (isInt4("4e2")!= true) throw '';
if (isInt4(" 1 ")!= true) throw '';
if (isInt4(""))     throw '';
if (isInt4("  "))   throw '';
if (isInt4(42.1))   throw '';
if (isInt4(null))   throw '';
if (isInt4(NaN))    throw '';
if (isInt4("1  a")) throw '';
if (isInt4("4e2a")) throw '';

Number.isInteger(val);