Function json_string 

pub fn json_string(text: &str) -> String

What: Encode text as a JSON string literal, exactly as JSON.stringify would. &str borrows the text; String is the owned, quoted result. Why: Messages contain file paths, quotes and user-written keys. Each character is encoded at this final step so no value can break out of its JSON string or its line: quotes, backslashes and every control character are escaped.

In TS you’d write (pseudocode):

function jsonString(text: string): string { return JSON.stringify(text); }