JavaScript - Explore the distinctions in defining an iteration variable using the let and var keywords within a for-loop

Can you explain the distinctiveness between utilizing a let in the body of a for loop and a var specifically within the JavaScript for loop? What are the differences in terms of functionality and why?

For instance:

When using let

for (let i = 0; i < 10; i++) {

}

When using var

for (var i = 0; i < 10; i++) {

}

Do these two methods operate similarly or have different mechanisms, and is one more efficient than the other?

Moreover, does this distinction extend to while loops and do-while loops as well?

javascriptfor-loopvarlet

Answer №1

let is specific to the block it's defined in, while var has broader scope. When using let, variables like i are limited to the forloop body. On the other hand, with var (whether function or globally scoped), you have more flexibility.

for (var j = 0; j < 10; j++) {

}

console.log(j);


for (let i = 0; i < 10; i++) {

}

console.log(i);

You can test out the for loop using var in your chrome console and observe that i becomes part of the window object.

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