Child blocks and parent borders(Grid-Layout)

Question

Why do child blocks (block) go beyond the boundaries of the parent block (child_block)? I would like child blocks to automatically wrap to a new line

How to achieve the result as in the screenshot:

let main = document.querySelector('.main_block');
let child_block = document.querySelector('.child_block');
            
for(let i = 0; i < 50; i++){
let xep = document.createElement('div'); 
child_block.prepend(xep);
xep.className = 'block';
xep.innerHTML = 'Xopa'
}

.main_block{
display:grid;
grid-template-columns: 100%; 
padding:10px;
margin:50px;
border:1px solid black;
}

.child_block{
display:grid;
grid-auto-flow: column;
}

.block{
display: inline-block;  
border:1px solid black;
font-size:18px;
padding:10px;
}

<div class = "main_block">

<div class = "child_block">


</div>

</div>

Answer 1

you can use this with flex too

let main = document.querySelector('.main_block');
let child_block = document.querySelector('.child_block');
            
for(let i = 0; i < 50; i++){
let xep = document.createElement('div'); 
child_block.prepend(xep);
xep.className = 'block';
xep.innerHTML = 'Xopa'
}

.main_block{
display:grid;
grid-template-columns: 100%; 
padding:10px;
margin:50px;
border:1px solid black;
}

.child_block{
display:flex;
flex-wrap: wrap;
}

.block{
display: inline-block;  
border:1px solid black;
font-size:18px;
padding:10px;
}

<div class = "main_block">

<div class = "child_block">


</div>

</div>

and with grid

let main = document.querySelector('.main_block');
let child_block = document.querySelector('.child_block');
            
for(let i = 0; i < 50; i++){
let xep = document.createElement('div'); 
child_block.prepend(xep);
xep.className = 'block';
xep.innerHTML = 'Xopa'
}

.main_block{
display:grid;
grid-template-columns: 100%; 
padding:10px;
margin:50px;
border:1px solid black;
}

.child_block{
display:grid;
grid-template-columns: repeat(auto-fill,minmax(50px,1fr));
}

.block{
display: inline-block;  
border:1px solid black;
font-size:18px;
padding:10px;
}

<div class = "main_block">

<div class = "child_block">


</div>

</div>