Set charset meta tag with JavaScript
You can't set the charset content attribute by setting the charset property because they don't reflect each other. In fact there is no property that reflects the charset content attribute.
The http-equiv content attribute is reflected by the httpEquiv property so
charsetMetaTag['httpEquiv'] = 'Content-Type';
would create the meta element correctly.
But none of this matters. The character set is established by the parser, so constructing the meta element in JavaScript after the HTML has been parsed will have no effect on the character set of the document at all.