How to Check if All Values are True in a JavaScript Array

If you ever need to check if an array only has true values in JavaScript, you can use Array.every in combination of the global Boolean object:

const validations = [
    true,
    false,
    '0',
    undefined
    null
];

const isEntirelyTrue = validations.every(Boolean);

// The above is equivalent to saying:
const isEntirelyTrue = validations.every(item => !!item);
const isEntirelyTrue = validations.every(item => item === true);
Copied to clipboard!

Explanation

The every method tests whether all elements in the array pass the test that is implemented in the callback function. It is exactly what we need for this purpose. It always returns a boolean value: either true or false.

Combining this with the global Boolean, which is a wrapper for boolean values, we can get the desired effect. It returns false if the value is one of:

[0, -0, null, false, NaN, undefined, '']
Copied to clipboard!

Any other value will produce true. It is equivalent of double negating a value to cast it to a boolean value, or comparing it to the boolean true.

How to Check if All Values are True in a JavaScript Array
If you would like to see more Webtips, follow @flowforfrank

Why Do You Need to Know About Functional Programming?

Resources:

Remove ads
Remove ads

๐Ÿ“š Get access to exclusive content

Want to get access to exclusive content? Support webtips with the price of a coffee to get access to tips, checklists, cheatsheets, and much more. โ˜•

Get access Support us
Remove ads Read more on
Remove ads
Remove ads
๐ŸŽ‰ Thank you for subscribing to our newsletter. x This site uses cookies We use cookies to understand visitors and create a better experience for you. By clicking on "Accept", you accept its use. To find out more, please see our privacy policy.