我智商爆棚
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import assertString from './util/assertString';
var notBase64 = /[^A-Z0-9+\/=]/i;
export default function isBase64(str) {
assertString(str);
var len = str.length;
if (!len || len % 4 !== 0 || notBase64.test(str)) {
return false;
}
var firstPaddingChar = str.indexOf('=');
return firstPaddingChar === -1 || firstPaddingChar === len - 1 || firstPaddingChar === len - 2 && str[len - 1] === '=';
}