Get all sub-arrays of array arr[] with sum k

getSubArraysOfSum.js

/* 
    References: 
    ==============

        1: HTTPS://WWW.QUORA.COM/WHAT-IS-THE-RECURSIVE-SOLUTION-FOR-FINDING-ALL-SUBSETS-OF-A-GIVEN-ARRAY

        2: HTTPS://WWW.IDESERVE.CO.IN/LEARN/GENERATE-ALL-SUBSETS-OF-A-SET-RECURSION
hellow world from emacs 
*/

function getSubArr (mainArr, index, sum) {
    let allSubArrays = [];
    let returnedSubArrays = [];
    
    if (index === 1) {
        // add fist element as sub-array
        let firstKey = [];
        firstKey.push(mainArr[0]);
        allSubArrays.push(firstKey);
	
        return allSubArrays;

    } else {

        returnedSubArrays = getSubArr(mainArr, index - 1);
        
        for (const arr of returnedSubArrays ) {
            
            allSubArrays.push(arr);			
            
            // deep cloing for the array
            //let concatWithKey = JSON.parse(JSON.stringify(arr));
            
            // shallow clone but will play nice with primitive data types
            let concatWithKey = arr.slice();
	    
	    concatWithKey.push(mainArr[index - 1]);
            allSubArrays.push(concatWithKey);
        }
        // add key item as sub-array
        let keyItem = [];
        keyItem.push(mainArr[index - 1]); // make it array of single element
        allSubArrays.push(keyItem);
	console.log(allSubArrays); // to print output on node console
        return allSubArrays;
    }
    
}

function findSubArr (mainArr, sum) {
    let allSubArr = getSubArr(mainArr, mainArr.length);
    let returnArr = [];
    for (let arr of allSubArr) {
        let total = arr.reduce( (a, b) => a + b); 

        if ( total === sum ) {
            returnArr.push(arr);
        }
    }

    console.log( returnArr );
}

const arr = [1,2,3,7,8];
const k = 11;
findSubArr(arr, k);