Introduction to JavaScript – Create a Variable: let

When you attempt to assign a value to a const variable like this example shows:

const myName = 'Seth';

myName = 'Hannah';

If you attempt the code above (assigning a value to a const variable) you will receive the following error:

TypeError: Assignment to constant variable.
JavaScript threw an error because you assigned a new value to a constant variable. Constant variables, as their name implies, are constant — you cannot assign them a different value.

Let variables, however, can be reassigned: (see code example below.)

let meal = 'Enchiladas';
console.log(meal);
meal = 'Tacos';
console.log(meal);
// output: Enchiladas
// output: Tacos

In the example above, the let keyword is used to create the meal variable with the string ‘Enchiladas‘ saved to it. On code line three (above), the meal variable is changed to store the string ‘Tacos‘.

You may be wondering, when to use const vs let. In general, only use const if the value saved to a variable does not change in your program.

Introduction to JavaScript – Create a Variable: let