JavaScript Compruebe si es indefinido o nulo
if( typeof myVar === 'undefined' || myVar === null ){
// myVar is undefined or null
}
Grepper
if( typeof myVar === 'undefined' || myVar === null ){
// myVar is undefined or null
}var myVar=null;
if(myVar === null){
//I am null;
}
if (typeof myVar === 'undefined'){
//myVar is undefined
}
if( value ) {
}