Use the VALUES() function

INSERT INTO t (t.a, t.b, t.c)
VALUES ('key1','key2','value'), ('key1','key3','value2')
ON DUPLICATE KEY UPDATE
t.c = VALUES(t.c)

see http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html

I tested the following and it seems to work:

INSERT INTO `places` (col1, col2, col3) VALUES
 ('aaa', NULL, 'eee'),
 ('ccc', 'ddd', 'fff')
ON DUPLICATE KEY UPDATE
 col1=COALESCE(VALUES(col1), col1),
 col2=COALESCE(VALUES(col2), col2),
 col3=COALESCE(VALUES(col3), col3);

In an ON DUPLICATE KEY statement, the VALUES(<col>) means "whatever I tried to insert in each row." So in the first row above, VALUES(col2) is NULL, and col2 is the value already stored on the row for that primary key.

The COALESCE() function returns its first non-NULL argument. So COALESCE(NULL, col2) returns the existing value for col2.

You do need to write out all the clauses for all these columns if you want to have them "default to previous" in this way.

P.S.: Your use of INSERT INTO places () is incorrect. The empty list of columns () must correspond to an empty list of values. I.e. the two lists must have the same number of terms.

I would try an array of objects

[
 {name:'Hy Dag3', points:'55040464', rank:'master', hotStreak:114,...},
 {name:'Hkj', points:'554064', rank:'novice', hotStreak:14,...}
]

and then

this.conn.query("INSERT summoners SET ? " +
" ON DUPLICATE KEY UPDATE name = VALUES(name), rank = VALUES(rank)...

Because according to doc:

var post  = {id: 1, title: 'Hello MySQL'};
var query = connection.query('INSERT INTO posts SET ?', post, function (error, results, fields) {
  if (error) throw error;
  // Neat!
});
console.log(query.sql); // INSERT INTO posts SET `id` = 1, `title` = 'Hello MySQL'

Beginning with MySQL 8.0.19 you can use an alias for that row (see reference).

INSERT INTO beautiful (name, age)
    VALUES
    ('Helen', 24),
    ('Katrina', 21),
    ('Samia', 22),
    ('Hui Ling', 25),
    ('Yumie', 29)
    AS new
ON DUPLICATE KEY UPDATE
    age = new.age
    ...

For earlier versions use the keyword VALUES (see reference, deprecated with MySQL 8.0.20).

INSERT INTO beautiful (name, age)
    VALUES
    ('Helen', 24),
    ('Katrina', 21),
    ('Samia', 22),
    ('Hui Ling', 25),
    ('Yumie', 29)
ON DUPLICATE KEY UPDATE
    age = VALUES(age),
     ...