Text input to have whatever left as width - css

Question

I want to have a Tags input (just like the stackoverflow's one) where users can type their chosen tags and it shows inside the input.
I decided to do it inside of a ul where the input is the last li:
<ul class="tag-box">
<li class="tags" *ngFor="let tag of tags">{{tag.name}}<a class="close"></a></li>
<li class="new-tag"><input class="input-tag" type="text"></li>
</ul>
But the problem is the width of the input is always small by default while I want it to take all the remaining width:
my css:
.tag-box {
list-style: none;
padding: 3px;
margin: 0;
display: inline-block;
font-family: arial;
width: 100%;
border: 1px solid #F39F19;
border-radius: 4px;
}
.tag-box li {
padding: 4px 6px;
float: left;
display: inline-block;
}
.tag-box li.tags {
background: #F1C617;
color: #fff;
border-radius: 4px;
margin: 4px 3px;
position: relative;
}
.tag-box li .input-tag {
color: #000;
height: 24px;
vertical-align: middle;
border: none;
outline: none;
background: none;
}
Is there a way where my input my input can take whatever left of space as width according to the loop?

Answer 1

Here's one way you could do it, I'm adding 3 things. You'll eventually want to give it a min-width and make it wrap though.
.tag-box {
display: flex;
}
.tag-box .new-tag {
flex: 1
}
.tag-box li .input-tag {
width: 100%;
}