The latest articles on DEV Community by Vaishali JS (@chakudi). https://dev.to/chakudi https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F586653%2Fe7364871-54b4-47df-b585-a347e6e7b9fe.jpg https://dev.to/chakudi en Vaishali JS Sun, 28 Feb 2021 09:18:00 +0000 https://dev.to/chakudi/lets-enter-the-temporal-dead-zone-3ald https://dev.to/chakudi/lets-enter-the-temporal-dead-zone-3ald <p>We are familiar with variable hoisting in JavaScript. If we try to access a variable (declared using <code>var</code> keyword) before assign it any value, we get <code>undefined</code>. But that's not the case with variables defined using <code>let</code> or <code>const</code>. If we try to access a variable (declared using <code>let</code> or <code>const</code>) before assigning it any value, we get <code>ReferenceError</code>.</p> <p>Many people believe the reason behind this behavior is that <code>let</code> and <code>const</code> are not hoisted, which is not true. Just like <code>var</code>, they are hoisted, but what they lack is the <em>initialization process</em> which <code>var</code> goes through but <code>let</code> and <code>const</code> do not.</p> <p>For <code>let</code> and <code>const</code>, initialization is only complete when a value is assigned to the variable; and the period from start of the block scope to initialization of value, where we receive <code>ReferenceError</code>, is known as the <em>Temporal Dead Zone</em>.</p> <p>Wrapping up: All <code>var</code>, <code>let</code> and <code>const</code> are hoisted. But, unlike <code>var</code>, <code>let</code> and <code>const</code> do not go though initialization process. The time (zone) from start of block scope to actual initialization is called Temporal Dead Zone 🐱‍👤.</p> javascript firstpost