<h1>item2にスペースを割り当てる</h1>
<div class="container">
    <div class="item">1</div>
    <div class="item item-flex-grow1">2</div>
    <div class="item">3</div>
    <div class="item">4</div>
</div>

<h1>item2, 3にスペースを割り当てる</h1>
<div class="container">
    <div class="item">1</div>
    <div class="item item-flex-grow2">2</div>
    <div class="item item-flex-grow3">3</div>
    <div class="item">4</div>
</div>

.container {
    width: 400px;
    background-color: #eee;
    display: flex;
}

.item {
    width: 50px;
    height: 50px;
}

.item-flex-grow1 {
    flex-grow: 1;
}

.item-flex-grow2 {
    flex-grow: 1;
}

.item-flex-grow3 {
    flex-grow: 2;
}

.item:nth-child(1) {
    background-color: #fff001;
}

.item:nth-child(2) {
    background-color: #00a5e7;
}

.item:nth-child(3) {
    background-color: #00984b;
}

.item:nth-child(4) {
    background-color: #cd5638;
}

External CSS

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External JavaScript

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