Day 34 of #100DaysOfCode: Review CSS-Three ways to center the HTML element

Introduction

The Review CSS series is the note for some common CSS usages. Three are three ways for centering the HTML element.

Method 1. Use relative/absolute, top/left, and margin

1. Use absolute and top/left to center the child component
2. Move back the child component with margin

Demo

Code

<div class="outer">
  <div class="inner">
    <p>center</p>
  </div>
</div>

.outer {
  background-color:green;
  position: relative;   
  height: 400px;
}
.inner {
  background-color: blue;
  position: absolute;   
  height: 100px;
  width: 200px;
  margin: -50px 0 0 -100px;  
  top: 50%;
  left: 50%;
}

Method 2. Use relative/absolute, top/left, and translate

1. Use absolute and top/left to center the child component
2. Move back the child component with translate

Demo

Code

.outer {
  background-color:green;
  position: relative;   
  height: 400px;
}
.inner {
  background-color: blue;
  position: absolute;   
  height: 100px;
  transform:translate(-50%,-50%); 
  top: 50%;
  left: 50%;
}

Method 3. [flexbox] use align-items and justify-content

Demo

Code

.vertical-container {
  height: 300px;
  display: -webkit-flex;
  display:         flex;
  -webkit-align-items: center;
          align-items: center;
  -webkit-justify-content: center;
          justify-content: center;
  background-color:green;
}

.center{
  background-color: blue;
}

That's it!

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