fix(guide): simplify directory structure

guide/english/javascript/rest-parameters/index.md

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+---
+title: Rest Parameters
+---
+
+## Rest Parameters
+In ES6, the rest paramter syntax `...` allows you to gather up an indefinite number of arguments into an array. 
+
+Even though they look the same, it does the opposite of the spread operator, which takes every item from an iterable and spreads them out into their individual values. 
+
+### Syntax
+
+```js
+function myFunc(...args) {
+  console.log(args);
+}
+
+myFunc( 1, 2, 3, 4, 5);       // [1,2,3,4,5]
+
+```
+
+You can prefix a function's last parameter with `...` when you want to do something with the initial paramters and then treat all of the remaining parameters differently. 
+
+```js
+function convertCurrency(rate, fee, ...amounts) {
+  return amounts.map(amount => (amount * rate) + fee);
+}
+
+convertCurrency(0.89, 2.5, 100, 250, 75, 150, 300); // [ 91.5, 225, 69.25, 136, 269.5 ]
+
+```
+
+The `...` lets you gather up the rest of the arguments, if there are any, into an array. 
+
+### The difference between rest parameters and the arguments object
+
+`arguments` is an array-like object, available inside functions, that contains the arguments passed to those functions. It's called "array-like" because it doesn't have all of an array's built in methods, such as `.forEach()` and `.map()`. 
+
+The rest parameters are an array, with all of the array methods included.