How to use the libsodium-wrappers.from_base64 function in libsodium-wrappers

function destringifyValue(v, t){
  if (t == 'string') return v;
  else if (t == 'number') return parseFloat(v);
  else if (t == 'boolean'){
    v = v.toLowerCase();
    if (!(v == 'true' || v == 'false')) throw new RangeError('Invalid stringified boolean value: ' + v);
    return v == 'true' ? true : false;
  } else if (t == 'date'){
    return new Date(parseInt(v));
  } else if (t == 'buffer') return libsodium.from_base64(v);
  else if (t == 'object') return JSON.parse(v);
  else throw new TypeError('Unsupported type: ' + t);
}

export function fromBase64(str: b64string): Uint8Array {
  if (typeof str !== 'string')
    throw new TypeError('"str" is not a string');

  return sodium.from_base64(str);
}

function fromB64URLSafe(str) {
  if (!(typeof str === 'string')) { throw new TypeError('Can only decode string'); }
  return Buffer.from(sodium.from_base64(str, sodium.base64_variants.URLSAFE_NO_PADDING));
}

constructor(key) {
		this.key = sodium.from_base64(key, sodium.base64_variants.URLSAFE_NO_PADDING);
	}

function b64dec (input) {
  return sodium.from_base64(input, sodium.base64_variants.URLSAFE)
}