Looking at using let and const vs using var, semantically

dont-use-var.js

function getNameWithLetAndConst(options) {
  // `name` scoped to its nearest parent block (here: the function-block)
  let name = 'Jill'
  
  if (options.test) {
    // `combined` is scoped to its nearest parent block (here: the if-block)
    // because of how block-scoping works, `name` is also available here
    const combined = `${name}-tested`   
    
    if (options.someCondition) {
      // the outer `name` is mutated (which let allows)
      name = combined
    }
  }
  
  // this will be `name` value, conditionally mutated within the nested if blocks
  return name
}

function getNameWithVar(options) {
  // `name` is scoped to its nearest parent function
  // QUESTION: how is this clearer than using `let` or `const` here?
  var name = 'Jill'
  
  if (options.test) {
    const combined = `${name}-tested`
    
    if (options.someCondition) {
      name = combined
    }
  }
    
  return name
}

onlyReasonForVar.js

// this is the only reason I can think of that using `var` would be more meaningful:

function omg(a, b) {
  
  if (a) {
    var value = a
  }
  
  if (b) {
    value = value ? value + b : b
  }
  
  return value
}

// except this is really confusing to look at (imo) and would almost certainly be rewritten as:

function omg(a, b) {
  var value
  
  if (a) {
    value = a
  }
  
  if (b) {
    value = value ? value + b : b
  }
  
  return value
}

// in which case why not just write:
function omg(a, b) {
  let value
  
  if (a) {
    value = a
  }
  
  if (b) {
    value = value ? value + b : b
  }
  
  return value
}