We were discussing the let keyword in the Part 1 of this
series. We discussed what the advantages and how we can use let keyword in the
code. However, let keyword has a problem it does not support hoisting, means if
you have declared a variable using let keyword in the mid of the block it would
not be available in the part above the declaration of the let keyword.
So you always make
sure that let is declared at the top of the block.
As we discussed earlier let keyword kind of Hack the scope
implicitly. We can always write the code to make sure when we see we can
explicitly identify that this block is a scope. The example given the in the
Part 1 of this series used the implicit way. To use the explicit way do it like
this
function foo(bar) {
"use
strict"
let (test = bar) {
console.log(test) // "bar"
}
console.log(baz)
// reference error
}
However, this syntax is rejected by the committee. we can use some other way to make sure we see the
block scope in the code as we read the code.
function foo(bar) {
"use
strict"
/*let */
{
let test = bar
console.log(test) // "bar"
}
console.log(baz)
// reference error
}
This is one way to do it. Keyle Simpson have
created this great tool to help you with block scoping it is called Let-er .
So, as we started to talk about tools you might want to take
a look at traceur-compiler it generates ES 5 code from ES 6 code. As there is development going on in ES 6
you should start writing your code in ES 6 and use a transpiler to convert
the ES 6 code to ES 5. You can use grunt-traceur . Other than this you might wanna take a look at the tools for ES 6.
Hoisting
Hoisting
Hoisting is a concept which is developed to understand how
JavaScript works when we declare the variables and functions. Take a look at
the code below
