Sass CSS: Target Parent Class from Child

How to target the parent class from nested classes in SASS

You could use parent selector and invert your nesting in sass

.group-left {
  .wrapper & {
    background-color: blue;
  }
  .wrapper-child:nth-child(2n+2) & {
    background: red;
  }
}

How to select parent pseudo-class from within child using scss

So seems like this is really easy. Whoops.

You just do the following:

SCSS:

.child {
    .parent:first-child & {
        height: 50px;
    }
}

This probably looks silly, but for my situation, it's actually useful.

Sass get parent or parent child

Is this logic useful?

Updated fiddle

SASS

.test{
    &-modifier{
        color: green;
    }

    &:hover &-modifier{
        color: red;        
    }
}

HTML

<div class="test">
  <div class="test-modifier">test</div>
</div>

Here is a couple of more variants based on the given comments

.test{
    &-modifier{
        color: green;
    }

    &-modifier2{
        color: green;
    }

    &:hover &-modifier,
    &:hover &-modifier2
    {
        color: red;        
    }}

.test{
    &-modifier{
        color: green;
    }

    &-modifier2{
        color: green;
    }

    &:hover &-modifier2 {
        color: red;        
    }
}

.test{
    &-modifier{
        color: green;
    }

    &-modifier2{
        color: green;
    }

    &-modifier2:hover {
        color: red;        
    }
}

SCSS modify parent selector

To make your last solution work, you can use @at-root.

body p {
  & {
    color: black;
  }
  @at-root #{selector-replace(&, "body", "body.other-mode")} {
    color: red;
  }
}

compiles to

body p {
  color: black;
}
body.other-mode p {
  color: red;
}

But personally, I find your original solution the most readable.

body { &.other-mode p {color: red;} }

I find the split body and p more convenient in SCSS.

Select parent selector in SASS/SCSS

Either you write both the selectors with the full classname (without using &) or you could save a reference to the .message class and use it in the nested selector

.message {

  display: block;
  width: 300px;
  border-radius: 5px;
  border: 2px solid #000;
  padding: 10px;

  $this: &; /* reference to the .message class */

  &__title {
    font-size: 18px;
    line-height: 1;
    color: #000;
    margin-bottom: 10px;
  }

  &__content {
    font-size: 15px;
    color: #000;
  }

  &--success {
    border-color: #3f9442;

    /* use the reference stored */

    #{$this}__title {
      color: #3f9442;
    }

    #{$this}__content {
      color: #3f9442;
    }
  }
}

Target the same child with two differents parent class

In your code, if you are using & it means that they are in the same element and in a single element there is only 1 ID. You should use a class in that situation.

#header {
    position: relative;
    width: 100%;

    &#header-g {
        position: fixed;
        top: 0;
        left: 0;
        z-index: 300;
        width: 100%;

but it should be something like this. #header and #header-gestion are you ID parents while they have the same children which are .l-header-top.

#header {
    position: relative;
    width: 100%;
    .l-header-top {
       height: 55px;
       line-height: 50px;
       border-top: 5px solid #474747;
       background-color: #f0f1f3;

       font-size: 16px;
    }
}

#header-g {
    position: fixed;
    top: 0;
    left: 0;
    z-index: 300;
    width: 100%;
    .l-header-top {
       height: 55px;
       line-height: 50px;
       border-top: 5px solid #474747;
       background-color: #f0f1f3;

       font-size: 16px;
    }
}

Or you use & in this way which is based on BEM Methodology in class naming conventions. You can check this link: BEM — Block Element Modifier Methodology

#header {
    position: relative;
    width: 100%;
    &-g {
       position: fixed;
       top: 0;
       left: 0;
       z-index: 300;
       width: 100%;
    }
}


#header,
#header-g {
    .l-header-top {
       height: 55px;
       line-height: 50px;
       border-top: 5px solid #474747;
       background-color: #f0f1f3;
       font-size: 16px;
    }
}