On 9/30/2013 3:51 PM, Dmitry Soshnikov wrote:
Just re-read meeting notes, OK, cool on two scopes (seems like they
are not in the spec yet). Want to double-check though: whether it will
be possible to transpile now to ES3? From what I've seen in the notes,
the head-scope will be able to access `this` value of the activation,
etc. Not sure how to transpile now. Could someone give an example of a
wrapper scope please, and confirm whether it's transpilable now?
I believe it is transpilable if you use an inner function scope. Someone
correct me if my translations are semantically incorrect:
ES6:
```js
var x = 1, y = 2;
function foo(x = 3, y = y, z = y) {
return [x, y, z];
}
```
ES3:
```js
var x = 1, y = 2;
function foo(x, y, z) {
// defaults
if (x === undefined) {
x = 3;
}
if (y === undefined) {
y = y; // essentially a no-op
}
if (z === undefined) {
z = y;
}
// body
return (function(x, y, z){
return [x, y, z];
}).call(this, x, y, z);
}
```
ES6:
```js
var x = 1, y=2;
function foo(x=3, y= (x = undefined, 4)) {
return [x,y];
}
```
ES3:
```js
var x = 1, y=2;
function foo(x, y) {
// defaults
if (x === undefined) {
x = 3;
}
if (y === undefined) {
y = (x = undefined, 4);
}
// body
return (function(x, y) {
return [x, y];
}).call(this, x, y);
}
```
ES6:
```js
function foo(bar = function() { return 'param-inner' }) {
var ret = bar();
function bar() {
return 'body-inner';
}
return ret;
}
```
ES3:
function foo(bar) {
// defaults
if (bar === undefined) {
bar = function() { return 'param-inner'; };
}
// body
return (function(bar){
var ret = bar();
function bar() {
return 'body-inner';
}
return ret;
}).call(this, bar);
}
A clearer example of my own which I think demonstrates the scoping
better (or exposes a problem with my understanding):
ES6
```js
function foo(x, y = function() { return x }) {
x++;
return x + y();
}
foo(1); // is this 3 or 4?
```
ES3:
```js
function foo(x, y) {
// defaults
if (y === undefined) {
y = function() { return x };
}
// body
return (function(x, y) {
x++;
return x + y();
}).call(this, x, y);
}
foo(1); // 3
```
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