demo/typescript.js
function findTokenOnLeftOfPosition(file, position) {
        // Ideally, getTokenAtPosition should return a token. However, it is currently
        // broken, so we do a check to make sure the result was indeed a token.
        var tokenAtPosition = getTokenAtPosition(file, position);
        if (isToken(tokenAtPosition) && position > tokenAtPosition.getStart(file) && position < tokenAtPosition.getEnd()) {
            return tokenAtPosition;
        }
        return findPrecedingToken(position, file);
    }
function findTokenOnLeftOfPosition(file, position) {
        // Ideally, getTokenAtPosition should return a token. However, it is currently
        // broken, so we do a check to make sure the result was indeed a token.
        var tokenAtPosition = getTokenAtPosition(file, position);
        if (isToken(tokenAtPosition) && position > tokenAtPosition.getStart(file) && position < tokenAtPosition.getEnd()) {
            return tokenAtPosition;
        }
        return findPrecedingToken(position, file);
    }
The token on the left of the position is the token that strictly includes the position
or sits to the left of the cursor if it is on a boundary. For example

fo|o               -> will return foo
foo <comment> |bar -> will return foo