Edit in JSFiddle

let outside = 'outside'; 
let text    = 'text outside';

{
  let inside = 'inside'; 
  let text   = 'text inside';
  
  document.getElementById('out1').textContent =  'in inside ' + inside + ' is visible';
  document.getElementById('out2').textContent =  'in inside ' + outside + ' is visible';
  document.getElementById('out3').textContent =  'in inside text is ' + text;
}

document.getElementById('out4').textContent =  'in outside ' + outside + ' is visible';
try {
	document.getElementById('out5').textContent =  'in outside ' + inside + ' is visible';
} catch(e) {
	document.getElementById('out5').textContent =  'in outside inside is not visible';
}
document.getElementById('out6').textContent =  'in outside text is ' + text;

<div id="out1"></div>
<div id="out2"></div>
<div id="out3"></div>
<div id="out4"></div>
<div id="out5"></div>
<div id="out6"></div>