What is the reasoning behind JavaScript hoisting variables?
Why did the designers choose to incorporate hoisting into JavaScript? Is this a feature found in other commonly used programming languages?
It would be helpful to include any pertinent links to official documentation or references for further information.
In his book "JavaScript Patterns," Stoyan Stefanov delves into the concept of hoisting, which is a product of the JavaScript interpreter's implementation.
When interpreting JS code, the interpreter goes through two passes. In the first pass, it handles variable and function declarations.
The second pass involves executing the actual code. Here, the interpreter deals with function expressions and undeclared variables.
Therefore, we can leverage the idea of "hoisting" to explain this type of behavior.
"Function hoisting unintentionally led to the phenomenon of variable hoisting due to the absence of block scope in JS and the rush nature of its development in 1995."
"Function hoisting facilitates top-down program organization, provides 'let rec' for free, allows calling functions before declaring them; variable hoisting came as a side effect."
https://i.sstatic.net/UJ8vo.png
I am not aware of any widely used languages that hoist variables like JavaScript does. Even ActionScript, which is another implementation of ECMAScript seen in Flash development, did not incorporate hoisting. This difference has caused confusion and frustration among developers transitioning from other languages to JavaScript.
The reason for this is that the javascript interpreter processes code in two stages.
During the first stage, all variable and function declarations are hoisted to the top of the function scope it is running in. This allows for the creation of variable objects for the execution context of the function before it is actually executed.
In the second phase, value assignments, code statements, and function calls occur line by line in the expected order.
To delve into more detail, you can read here.
This will provide a deeper understanding of the behavior related to let, const, and class declarations, as well as the precedence between variables and functions.
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