Run anon apex repeatedly when you have too many records to update in one transaction

exec-anon.js

var jsforce = require('jsforce');
var conn = new jsforce.Connection({
    serverUrl : '',
    sessionId : ''
});
var apexBody = `

update [
    select id
    from task
    where IsClosed = true
    and WhoId in (
        select id
        from lead
        where convertedcontactid = null
        and last_owner_activity_date__c = null
        and calls__c > 0
    )
    and lead__c = null
    and activitydate >= last_year
    and lastmodifieddate < today
    limit 1000
];

`;

function exec () {
    conn.tooling.executeAnonymous(apexBody, function(err, res) {
        if (err) { return console.error(err); }
        console.log("compiled?: " + res.compiled); // compiled successfully
        console.log("executed?: " + res.success); // executed successfully
        exec ();
    });
}

exec();