vars-on-top.md

Pattern: var declaration not at top of scope

Issue: -

Description

Due to variable hoisting in JavaScript, var declarations should be placed at the top of their scope to make the behavior explicit. This improves code clarity by making it obvious where variables are accessible from.

Examples

Example of incorrect code:

function doSomething() {
  console.log(a);
  if (condition) {
    var a = true;
  }
  var b = false;
}

f();
var x;

function test() {
  for (var i = 0; i < 10; i++) {}
  var y = 1;
}

Example of correct code:

function doSomething() {
  var a;
  var b;
  
  console.log(a);
  if (condition) {
    a = true;
  }
  b = false;
}

var x;
f();

function test() {
  var i;
  var y;
  
  for (i = 0; i < 10; i++) {}
  y = 1;
}