block-scoped-var.md

Treat var as Block Scoped (block-scoped-var)

This rule treats variables which are defined with var declarations as the same behavior as variables which are defined with let declarations.

Please turn no-redeclare rule off if you use this rule.

Rule Details

This rule aims to flag below about variables which are defined with var declaration:

• References from outside of the block which declare the variable.
• Re-declarations in a same block.
• Shadowing in a same function scope.

The following patterns are considered warnings:

{
  var a = 0;
}
console.log(a); // not defined.

for (var a = 0;;) {
}
console.log(a); // not defined.

var a = 0;
var a = 0; // already defined.

for (var a = 0;;) {
  var a = 0; // already defined.
}

function foo(a) {
  var a = 0; // already defined.
}

var a = 0;
{
  var a = 0; // already defined in the upper scope.
}

function foo(a) {
  if (Math.random() < 0.5) {
    var a = 0; // already defined in the upper scope.
  }
}

The following patterns are not considered warnings:

if (Math.random() < 0.5) {
  var a = 0;
  console.log(a);
}
else {
  var a = 1;
  console.log(a);
}