How to replace all undefined values in an array with "-"?

Question

I have an array like:

var array = [1, 2, undefined, undefined, 7, undefined]

and need to replace all undefined values with "-". The result should be:

var resultArray = [1, 2, "-", "-", 7, "-"]

I think there is a simple solution, but I couldn't find one.

Answer 1

You could check for undefined and take '-', otherwise the value and use Array#map for getting a new array.

var array = [1, 2, undefined, undefined, 7, undefined],
    result = array.map(v => v === undefined ? '-' : v);
    
console.log(result);

For a sparse array, you need to iterate all indices and check the values.

var array = [1, 2, , , 7, ,],
    result = Array.from(array, v => v === undefined ? '-' : v);
    
console.log(result);