Standard function to check for null, undefined, or blank variables in JavaScript?

Question

Is there a universal JavaScript function that checks that a variable has a value and ensures that it's not undefined or null? I've got this code, but I'm not sure if it covers all cases:

function isEmpty(val){
    return (val === undefined || val == null || val.length <= 0) ? true : false;
}

Answer

You can just check if the variable has a truthy value or not. That means

if( value ) {
}

will evaluate to true if value is not:

• null
• undefined
• NaN
• empty string ("")
• 0
• false