if (boo) {
// do something
}

while (boo) {
// do something
}

console.log( false == null ) // false
console.log( false == undefined ) // false
console.log( false == 0 ) // true
console.log( false == '' ) // true
console.log( false == NaN ) // false

console.log( null == undefined ) // true
console.log( null == 0 ) // false
console.log( null == '' ) // false
console.log( null == NaN ) // false

console.log( undefined == 0) // false
console.log( undefined == '') // false
console.log( undefined == NaN) // false

console.log( 0 == '' ) // true
console.log( 0 == NaN ) // false