Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class='flexContainer height'>
  <div>Item</div>
</div>

SassMeister-input.scss

// ----
// Sass (v3.3.14)
// Compass (v1.0.1)
// ----

@mixin flexContainer ($flex-direction: row, $flex-wrap: wrap, $align-items: center, $justify-content: center) {
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;

  // row / column
  -ms-flex-direction: $flex-direction;
  -webkit-flex-direction: $flex-direction;
  flex-direction: $flex-direction;

  // wrap / no-wrap
  -ms-flex-wrap: $flex-wrap;
  -webkit-flex-wrap: $flex-wrap;
  flex-wrap: $flex-wrap;

  // align cross axis
  -ms-flex-align: $align-items;
  -webkit-align-items: $align-items;
  align-items: $align-items;

  // align axis
  -ms-flex-pack: $justify-content;
  -webkit-justify-content: $justify-content;
  justify-content: $justify-content;
}

.flexContainer {
  @include flexContainer(row, no-wrap, center, center)  
}


.height {
  height: 300px;
  height: 90vh;
}

SassMeister-output.css

.flexContainer {
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  -ms-flex-direction: row;
  -webkit-flex-direction: row;
  flex-direction: row;
  -ms-flex-wrap: no-wrap;
  -webkit-flex-wrap: no-wrap;
  flex-wrap: no-wrap;
  -ms-flex-align: center;
  -webkit-align-items: center;
  align-items: center;
  -ms-flex-pack: center;
  -webkit-justify-content: center;
  justify-content: center;
}

.height {
  height: 300px;
  height: 90vh;
}

SassMeister-rendered.html

<div class='flexContainer height'>
  <div>Item</div>
</div>