typeof is not able to return the datatype in LWC .js

Question

I have used lwc data table and have set columns as below.

const columns = [
{label: 'Name', fieldName: 'Name', type: 'text', sortable: true},
{label: 'Active', fieldName: 'active', type: 'boolean', sortable: true}
];

then over a sort function I am getting the fieldName and tryoing to sort.

if(typeof fieldname === 'string'){
        data.sort((a,b) => {
            let valueA = key(a) ? key(a).toLowerCase() : '';
            let valueB = key(b) ? key(b).toLowerCase() : '';
            return reverse * ((valueA > valueB) - (valueB > valueA));
        });
    }else{
        data.sort(function(a,b){
            var a = key(a) ? key(a) : '';
            var b = key(b) ? key(b) : '';
            return reverse * ((a>b) - (b>a));
        });
    }

"if(typeof fieldname === 'string')" is always returning data type as string and not returning the Active field as boolean.

Basically I am trying to implement sort function where I am trying to sort text and checkbox values.

Answer 1

The typeof operator returns the evaluated type of variable passed in (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/typeof)

In your case, you're passing in a value of fieldName which is, in truth, string for both your columns:

const columns = [
{label: 'Name', fieldName: 'Name', type: 'text', sortable: true},
{label: 'Active', fieldName: 'active', type: 'boolean', sortable: true}
];

typeof columns[0] /// 'string'
typeof columns[1] /// 'string'

What you meant to do was check if columns[index].type equals to your expected data, e.g. like so

// it is not clear where you get fieldName from, so might as well get type there, too
if(type === 'string'){ 
        // do whatever
    }else{
       // do whatever again
    }

Further, as you noted in your comments, your sorting methods are very close and can be merged like so:

function valueConverter(val) => val ? (typeof val === 'string' ? val : val.toString()).toLowerCase() : '';

  data.sort((a,b) => {
            let valueA = valueConverter(key(a));
            let valueB = valueConverter(key(b));
            return reverse * ((valueA > valueB) - (valueB > valueA));
        });