Converts the characters "&", "<", ">", '"', and "'" in string to their corresponding HTML entities.

Note: No other characters are escaped. To escape additional characters use a third-party library like he.

Though the ">" character is escaped for symmetry, characters like ">" and "/" don't need escaping in HTML and have no special meaning unless they're part of a tag or unquoted attribute value. See Mathias Bynens's article (under "semi-related fun fact") for more details.

When working with HTML you should always quote attribute values to reduce XSS vectors.