align div center using flex code example

Example 1: css flex center

display: flex;
align-items: center;
justify-content: center;

Example 2: flex align children to side

flex-direction: column;
align-items: flex-start; //left
align-items: center; //center
align-items: flex-end; //right

Example 3: center flex

.flex-container {
  display: flex;
  height: 300px;
  justify-content: 
  center;
  align-items: center;
}