I am trying to create a helper function that will promisify a function that takes an arbitrary number of arguments. Intuitively, the problem might be tackled by wrapping resolve with callbacks, which I've always struggled with, so please tell me explicitly how do so. Thanks.

function prom(rawFunc, ...arg){
    // This is the helper function
    return new Promise ((resolve, reject)=>{
        checkFn(rawFunc);
        function checkFn(rawFunc){
            if (rawFunc instanceof Function === false){
                return reject("Error: rawFunc passed is not a function");
            } 
            let returnValue = rawFunc(...arg)
            resolve(returnValue);
        }
    });
}

function targetFn1 (a, b){
    console.log(`targetFn1 should return ${a+b}`)
    setTimeout(() => {
        console.log(`truly returning value ${a+b}`)
        return a + b 
    }, 4000);
    // this function returns a+b after a delay of 4 seconds
}

function targetFn2 (c, d, e){
    console.log(c)
    console.log(d)
    console.log(e)
    console.log(`targetFn2 returning ${c+d+e}`)
    return c+d+e
}

async function mainFn(){
    let value1 = await prom(targetFn1,1,3)
    let value2 = await prom(targetFn2,value1,3,4);
}

mainFn();


// console log :
// targetFn1 should return 4
// undefined
// 3
// 4
// targetFn2 returning NaN
// truly returning value 4