What is the difference between the usage of let and var in JavaScript?

Let in What is the difference between the usage of let and var in JavaScript? is used to limit the scope of variables to blocks. If you use var to declare a variable, the scope will be in function units. In this article, we will introduce the specific differences between let and var in What is the difference between the usage of let and var in JavaScript?. Below we Let’s look at the specific content.

Here we first talk about how to use let.

let is used when declaring variables.

Let’s look at the following code

let num = 123;
console.log(num);
{
    let num = 456;
    console.log(num);
}
console.log(num);

The execution results are as follows

123
456
123

According to the above execution results, we can confirm that the scope of the variable is limited to the block.

Next let’s look at the difference between the use of var and the above use of let

var is the variable scope in the function

Let’s look at the following code

var num = 123;
console.log(num);
{
    var num = 456;
    console.log(num);
}
console.log(num);

Execution results

123
456
456

According to the above execution results we can confirm that the scope of the variable is outside the block.

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