Nodejs block when iterating for 1 million records

Question

/* * This function is written to get data in big size (in Mb i.e. around 143 MB) as input and chunk it in 30 MB and perform the next operation... * using 'object-sizeof' npm module to calculate size on every iteration */

const Q = require('q');
const sizeof = require('object-sizeof');

function insertProcess(formattedData){
    let deferred = Q.defer();
    let finalData = [];
    // here data limit is 30 mb i.e. out of 143 mb want to send data 30 mb at time 
    let dataLimit = 30;
    
    if ((sizeof(formattedData) / 1000000) <= dataLimit) {
        
        // some function invoked 
        deferred.resolve();
    }
    else {
        async.forEachLimit(formattedData, 1000, (element, callback) => {

            finalData.push(element);
           
            if ((sizeof(finalData) / 1000000) >= dataLimit) {
            
                // passing finaldata to another function 
                // removing all element from finalData by setting its length to 0               
                finalData.length = 0;
                callback();
            }
            
        }, (error) => {
        
            if (finalData.length) {
                
                // passing finaldata to another function 
                // removing all element from finalData by setting its length to 0               
                finalData.length = 0;
                deferred.resolve();
            }
            
        })
    }
    return deferred.promise;
}