163 lines
5.2 KiB
Markdown
163 lines
5.2 KiB
Markdown
---
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title: Grid System
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---
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## Grid System
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In a nutshell, Bootstrap grid system helps you create mobile-first layouts. Mobile first means that the grid layout will automatically be responsive for smaller screens. The HTML then defines the grid layout for larger screens. It comprises of a system of rows and columns to help you structure your content.
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Rows are horizontal groups of columns, and each page has a maximum of 12 columns per row. Within each row, the content is placed inside the columns and it can span anywhere between 1 to 12 columns.
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Bootstrap has five different types of grid tiers: Extra small, Small, Medium, Large, and Extra large. There is a breakpoint defined for each of these grid tiers.
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Bootstrap uses pixels to define the grid tier breakpoints.
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#### How it works
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###### Container
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The container is the outer most element that *contains* your grid. Use `container` for a fixed-width container in the middle of the screen (add an extra margin on larger screens) or `container-fluid` for full width.
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```
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<div class="container"></div>
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```
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###### Row
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Use `row` to group your columns. This will keep everything lined up properly and help you structure your grid.
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```
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<div class="row"></div>
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```
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###### Columns
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Column classes indicate the number of columns you’d like to use out of the possible 12 per row. For example `col-sm-6` would mean your columns use up half the width of the `row` on a small screen, and `col-lg-4` would use up a third on a large screen.
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Here is how you would define a class prefix to use up one column width on the various screen sizes:
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- **Extra Small** `col-1`
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- **Small** `col-sm-1`
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- **Medium** `col-md-1`
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- **Large** `col-lg-1`
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- **Extra Large** `col-xl-1`
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```
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<div class="col-sm-1"></div>
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```
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#### Example
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A full width grid that has four columns, each taking up a full row on xs screens, half a row on sm and md screens, and a quarter of the width of the row on screens that are large and above:
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```
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<div class="container-fluid">
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<div class="row">
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<div class="col-12 col-sm-6 col-lg-4">First Column</div>
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<div class="col-12 col-sm-6 col-lg-4">Second Column</div>
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<div class="col-12 col-sm-6 col-lg-4">Third Column</div>
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<div class="col-12 col-sm-6 col-lg-4">Forth Column</div>
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</div>
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</div>
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```
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*Note that `col-md` and `col-xl` are not defined, where a size is not defined, it will default down to the next smaller size that has been specified.*
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Bootstrap provides a ready-made 12 column grid system for use in layouts. Consider the following code.
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```html
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<div class="container">
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<div class="row">
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<div class="col-md-6">Content</div>
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<div class="col-md-6">Content</div>
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<div>
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</div>
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```
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where:
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- col = column
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- md = screen size
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- 6 = column width
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As a 12 column grid system, all user defined grid column widths must add up to 12.
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Screen size values can be assigned as follows:
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- xs - < 768px Phones
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- sm - < 992px Tablets
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- md - < 1200px Laptops
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- lg - > 1200px Desktops
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The following code and image shows what is possible using different column widths.
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```html
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<div class="container">
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<div class="row">
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<div class="example col-md-6">Content</div>
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<div class="example col-md-6">Content</div>
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<div>
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</div>
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<div class="container">
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<div class="row">
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<div class="example col-md-4">Content</div>
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<div class="example col-md-4">Content</div>
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<div class="example col-md-4">Content</div>
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<div>
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</div>
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<div class="container">
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<div class="row">
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<div class="example col-md-3">Content</div>
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<div class="example col-md-3">Content</div>
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<div class="example col-md-3">Content</div>
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<div class="example col-md-3">Content</div>
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<div>
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</div>
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<div class="container">
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<div class="row">
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<div class="example col-md-2">Content</div>
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<div class="example col-md-2">Content</div>
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<div class="example col-md-2">Content</div>
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<div class="example col-md-2">Content</div>
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<div class="example col-md-2">Content</div>
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<div class="example col-md-2">Content</div>
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<div>
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</div>
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<div class="container">
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<div class="row">
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<div class="example col-md-1">Content</div>
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<div class="example col-md-1">Content</div>
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<div class="example col-md-1">Content</div>
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<div class="example col-md-1">Content</div>
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<div class="example col-md-1">Content</div>
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<div class="example col-md-1">Content</div>
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<div class="example col-md-1">Content</div>
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<div class="example col-md-1">Content</div>
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<div class="example col-md-1">Content</div>
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<div class="example col-md-1">Content</div>
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<div class="example col-md-1">Content</div>
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<div class="example col-md-1">Content</div>
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</div>
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</div>
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```
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![12-col-grid](https://github.com/bflatt72/bflatt72.github.io/blob/master/img/bootstrapgrid1.png)
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#### More Information:
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<a href='https://getbootstrap.com/docs/4.0/layout/grid/' target='_blank' rel='nofollow'>Bootstrap Docs - Grid system</a>
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*This guide is based on Bootstrap v4 (it will work with v3 except extra small screens are defined as `xs` and there is no `xl` size)*
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* Extra large: **Viewport width >= 1200px**
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* Large: **Viewport width >= 992px**
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* Medium: **Viewport width >= 768px**
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* Small: **Viewport width >= 576px**
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* Extra small: **Viewport widths below 576px**
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#### More Information:
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https://getbootstrap.com/docs/4.0/layout/grid/
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