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Ilya Kantor 2019-07-31 23:18:20 +03:00
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1-js/06-advanced-functions/07-new-function/article.md
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@ -46,14 +46,13 @@ It is used in very specific cases, like when we receive code from a server, or t
## Closure
Usually, a function remembers where it was born in the special property `[[Environment]]`. It references the Lexical Environment from where it's created.
Usually, a function remembers where it was born in the special property `[[Environment]]`. It references the Lexical Environment from where it's created (we covered that in the chapter <info:closure>).
But when a function is created using `new Function`, its `[[Environment]]` references not the current Lexical Environment, but instead the global one.
But when a function is created using `new Function`, its `[[Environment]]` is set to reference not the current Lexical Environment, but the global one.
So, such function doesn't have access to outer variables, only to the global ones.
```js run
function getFunc() {
let value = "test";
@ -99,6 +98,8 @@ So if `new Function` had access to outer variables, it would be unable to find r
**If `new Function` had access to outer variables, it would have problems with minifiers.**
Besides, such code would be architecturally bad and prone to errors.
To pass something to a function, created as `new Function`, we should use its arguments.
## Summary
@ -111,7 +112,7 @@ let func = new Function ([arg1, arg2, ...argN], functionBody);
For historical reasons, arguments can also be given as a comma-separated list.
These three lines mean the same:
These three declarations mean the same:
```js
new Function('a', 'b', 'return a + b'); // basic syntax
@ -119,4 +120,4 @@ new Function('a,b', 'return a + b'); // comma-separated
new Function('a , b', 'return a + b'); // comma-separated with spaces
```
Functions created with `new Function`, have `[[Environment]]` referencing the global Lexical Environment, not the outer one. Hence, they cannot use outer variables. But that's actually good, because it saves us from errors. Passing parameters explicitly is a much better method architecturally and causes no problems with minifiers.
Functions created with `new Function`, have `[[Environment]]` referencing the global Lexical Environment, not the outer one. Hence, they cannot use outer variables. But that's actually good, because it insures us from errors. Passing parameters explicitly is a much better method architecturally and causes no problems with minifiers.