This traditional JS code works fine:

function staircase(n) { var line = Array(n + 1).fill(' '); line[n] = ''; for (var i = n - 1; i >= 0; i--) { line[i] = '#'; console.log(line.join('')); } } 

and ES6 we can write:

const staircase = n => { const line = Array(n + 1).fill(' '); line[n] = ''; for (let i = n - 1; i >= 0; i--) { line[i] = '#'; console.log(line.join('')); } } 

If our given input is 6 the output should be:

 # ## ### #### ##### ###### 

This traditional Javascript code works fine:

function staircase(n) { var line = Array(n + 1).fill(' '); //line[n] = ''; for (var i = n - 1; i >= 0; i--) { line[i] = '#'; console.log(line.join('')); } } 

and ES6 we can write:

const staircase = n => { const line = Array(n + 1).fill(' '); //line[n] = '';  for (let i = n - 1; i >= 0; i--) { line[i] = '#'; console.log(line.join('')); } } 

If our given input is 6 the output should be:

 # ## ### #### ##### ######