Fix english in style_guide_js.md

doc/development/fe_guide/style_guide_js.md

@@ -210,7 +210,7 @@ Do not use them anymore and feel free to remove them when refactoring legacy cod
 1. Avoid constructors with side-effects.
 Although we aim for code without side-effects we need some side-effects for our code to run.
 
-If the class won't do anything if we only instantiate it, it's ok to add side effects into the constructor (_Note:_ The following it's just an example. If the all purpose of the class is to add an event listener and handle the callback a function will be more suitable.)
+If the class won't do anything if we only instantiate it, it's ok to add side effects into the constructor (_Note:_ The following is just an example. If the only purpose of the class is to add an event listener and handle the callback a function will be more suitable.)
 
 ```javascript
 // Bad
@@ -236,7 +236,7 @@ export class Foo {
 }
 ```
 
-On the other hand, if a class only needs to extend a third party/add event listeners in some specific cases, they should be inited oustside of the constructor.
+On the other hand, if a class only needs to extend a third party/add event listeners in some specific cases, they should be initialized oustside of the constructor.
 
 1. Prefer `.map`, `.reduce` or `.filter` over `.forEach`
 A forEach will most likely cause side effects, it will be mutating the array being iterated. Prefer using `.map`,