Determine if string is in base64 using JavaScript

Question

I'm using the window.atob('string') function to decode a string from base64 to a string. Now I wonder, is there any way to check that 'string' is actually valid base64? I would like to be notified if the string is not base64 so I can perform a different action.

question from:https://stackoverflow.com/questions/7860392/determine-if-string-is-in-base64-using-javascript

Answer 1

If you want to check whether it can be decoded or not, you can simply try decoding it and see whether it failed:

try {
    window.atob(str);
} catch(e) {
    // something failed

    // if you want to be specific and only catch the error which means
    // the base 64 was invalid, then check for 'e.code === 5'.
    // (because 'DOMException.INVALID_CHARACTER_ERR === 5')
}