Is there a 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,

Answer 1

A solution I like a lot:

Let's define that a blank variable is null, or undefined, or if it has length, it is zero, or if it is an object, it has no keys:

function isEmpty (value) {
  return (
    // null or undefined
    (value == null) ||

    // has length and it's zero
    (value.hasOwnProperty('length') && value.length === 0) ||

    // is an Object and has no keys
    (value.constructor === Object && Object.keys(value).length === 0)
  )
}

Returns:

• true: undefined, null, "", [], {}
• false: true, false, 1, 0, -1, "foo", [1, 2, 3], { foo: 1 }