[css] flex property

{
    flex: /* */
}

HTML

<p>.container1</p>
<div class="container container1">
    <div class="box box1">.box1</div>
    <div class="box box2">.box2</div>
    <div class="box box3">.box3</div>
</div>

<p>.container2</p>
<div class="container container2">
    <div class="box box1">.box1</div>
    <div class="box box2">.box2</div>
    <div class="box box3">.box3</div>
</div>

CSS

.container {
    border: 1px solid gray;
    padding: 10px;
    height: 200px;
}

.container1 {
    display: flex;
    /* flex-direction: row; */
}

.container2 {
    display: flex;
    flex-direction: column;
}

.box {
    border: 1px solid gray;
    padding: 2px;
}

.box1 {
    background-color: lightskyblue;
}

.box2 {
    background-color: lightskyblue;
    flex: 1;
}

.box3 {
    background-color: lightskyblue;
}

 

https://www.w3schools.com/cssref/css3_pr_flex.asp

CSS flex property

 

https://developer.mozilla.org/ko/docs/Web/CSS/flex

flex - CSS: Cascading Style Sheets | MDN