Get unique keys from multiple objects

Question

If I have an array of objects like this:

var mountains = [
    { name: \'Kebnekaise\', elevation: 2106 },
    { name: \'Mount Ngauruhoe\', elevation: 2291, c         


        

Answer 1

Using ES6, one could do

var unique = new Set([].concat.apply([],mountains.map(Object.keys)))

Without ES6, something like

var unique = [].concat.apply([],mountains.map(Object.keys)).filter(function(value,i,arr) {
    return arr.indexOf(value) === i;
});